Amicus Curiae Brief — Gill v. Whitford, 138 S. Ct. 52 (2017) (No. 16-1161)

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AUG 10 2017

No. 16-1161 | OFFICE OF THE CLERK

IN THE

Supreme Court of the United States

BEVERLY R. GILL, ET AL.,

Appellants,

Vv.

WILLIAM WHITFORD, ET AL.,

Appellees.

ON APPEAL FROM THE UNITED STATES DISTRICT COURT

For THE WESTERN DISTRICT OF WISCONSIN

BRIEF OF BERNARD GROFMAN AND

RONALD KEITH GADDIE AS AMICI CURIAE

IN SUPPORT OF NEITHER PARTY

Thomas M. Bondy E. Joshua Rosenkranz

Avi Daniel Rosenblit Counsel of Record

ORRICK, HERRINGTON & Rachel Wainer Apter

SUTCLIFFE LLP Hannah Garden-Monheit

1152 15th Street NW ORRICK, HERRINGTON &

Washington, DC 20005 SUTCLIFFE LLP

51 West 52nd Street

New York, NY 10019

(212) 506-5000

jrosenkranz@orrick.com

Counsel for Amici Curiae

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I. Courts Must Provide A Check On

Egregious Partisan Gerrymandering.......

II. A Justiciable Partisan

TABLE OF CONTENTS

Gerrymandering Claim Requires Proof

Of Partisan Asymmetry, Lack Of

Responsiveness, And Causation...............

A. Partisan asymmetry means

there is a disparate impact on

voters based on political

SURE DS bi

B. Lack of responsiveness means

the ordinary political process

cannot provide a remedy................

C. Causation means that the

partisan asymmetry is a result

of invidious discrimination, not

neutral factors or chance................

eeerreeew ee eee ee ree aer ee eee

ITI. The Court Has Never Before

Confronted Reliable Evidence Of

These Three Discrete Elements................. 22

A. Bandemer, Vieth, and LULAC

did not consider evidence of

partisan asymmetry, lack of

responsiveness, and causation........ 23

B. The analytical tools for

evaluating these three elements

have dramatically improved

since Bandemer, Vieth, and

ill

TABLE OF AUTHORITIES

Page(s)

Cases

Abrams v. Johnson,

EE Ne ED 3

Ariz. State Legislature v. Ariz. Indep.

Redistricting Comm'n,

I a cc cceschssbedendondenenceosnenss 3

Badham uv. Eu,

694 F. Supp. 664 (N.D. Cal. 1988)........................ 2

Baldus v. Members of Wisc. Gov't

Accountability Bd.,

849 F. Supp. 2d 840

a a a ee 4

Bartlett v. Strickland,

a sniciicacinterinnsscbewniivntiionatadinenreislicguiiian 22

Brown v. Thomson,

a tiietancad 22

Bush v. Vera,

EEN I Re RE Se oe, 3

Cox v. Larios,

IRR EEA EOE a ne Me er 4

Davis v. Bandemer,

478 U.S. 109 (1986)...... 2, 3, 7, 8, 13, 16, 23, 24, 29

Gaffney v. Cummings,

I ccheaebenenaniinene 18

Georgia v. Ashcroft,

Re Ae pet 3

Holder v. Hall,

SLED LLM ALLE 3

Johnson v. De Grandy,

8 EEE nes RON See 3

League of United Latin American

Citizens (LULAC) v. Perry,

548 U.S. 399 (2006)............ 3, 21, 23, 25, 26, 28, 29

Miller v. Johnson,

I ceeunaieiiaioanen 3

Page v. Va. State Bd. of Elections,

No. 3:13-CV-678, 2015 WL 3604029

Ss ns MI Mis, HIE isicentadcinciuintccnesecacoucesecesenecses 3

Shaw v. Hunt,

i ccuueeslinions “dil 3

Shaw v. Reno,

A RT ae 3

Shelby County, Alabma v. Holder,

a i satiabiciinaanlanee 3

Thornburg v. Gingles,

RI i ce a oe ee a 3

Vieth v. Jubelirer,

EE Sees Ee passim

Other Authorities

Amici Br. of Prof. Gary King et al.,

League of United Latin American

Citizens (LULAC) v. Perry, Nos. 5-

204, 5-254, 5-276, 5-439, 2006 WL

NS CNG SIU BI orcnenns nc cnccesssccsessacssasns 26

Amicus Br. of Samuel S. Wang,

Harris v. Ariz. Indep.

Redistricting Comm'n,

No. 14-232, 2015 WL 6774017

a otepisonaaiiie 27

Charles S. Bullock, LI, & Ronald Keith

Gaddie, The Triumph of Voting

Rights in the South (2009)..............c00-s0-s0-+0-e00- 2,19

Charles S. Bullock, III, Ronald Keith

Gaddie, & Justin J. Wert, The Rise

and Fall of the Voting Rights Act

FRE iad ae EE ec AE sls GEES AEE no oe MEO 1

Jowei Chen, The Impact of Political Ge-

ography on Wisconsin Redistricting:

An Analysis of Wisconsin’s Act 42

Assembly Districting Plan,

Election L.J. (forthcoming 2017),

https://tinyurl.com/y7ohowmy ...............2..-..--<-.++ 31

Jowei Chen & Jonathan Rodden,

Cutting Through the Thicket:

Redistricting Simulations and the

Detection of Partisan Gerrymanders,

14 Election L.J. 312 (2015)...................... 19, 21, 30

Wendy Tam Cho et al., A Reasonable

Bias Approach to Gerrymandering:

Using Automated Plan Generation to

Evaluate Redistricting Proposals, 59

William & Mary L. Rev. (forthcom-

Ronald Keith Gaddie & Charles S.

Bullock, III, Elections to Open Seats

in the U.S. House: Where the Action

Teen enn ee eae cacadmmmahowanennniciey 2

Ronald Keith Gaddie & Charles S.

Bullock, III, From Ashcroft To

Larios: Recent Redistricting Lessons

from Georgia,

34 Fordham Urb. L.J. 997 (2007)............ iain tea 2

Bernard Grofman, Criteria for

Districting: A Social Science

Perspective,

Gg a Ss | Spe 20, 24

Bernard Grofman, Measures of Bias

and Proportionality in

Seats- Votes Relationships,

9 Pol. Methodology 295 (1983) ...................ccceceeeees 1

vil

Bernard Grofman & Thomas L. Brunell,

The Art of the Dummymander: The

Impact of Recent Redistrictings on

the Partisan Makeup of Southern

House Seats 183 (Peter Galderisi ed.,

Bernard Grofman & Gary King, The

Future of Partisan Symmetry as a

Judicial Test for Partisan

Gerrymandering after

LULAC v. Perry,

6 Election L.J. 2 (2007)............ 1, 12, 13, 14, 17, 18

Bernard Grofman, William Koetzle &

Thomas Brunell, An Integrated

Perspective on the Three Potential

Sources of Partisan Bias:

Malapportionment, Turnout

Differences, and the Geographic

Distribution of Party Vote Shares,

6 Electoral Stud. 467 (1997)...............0..ccccssecsesseese 1

Bernard Grofman, Michael Migalski &

Nicholas Noviello, The “Totality of

Circumstances Test” in Section 2 of

the 1982 Extension of the Voting

Rights Act: A Social Science

Perspective, 7 L. & Pol’y 199 (1985) ..................... 1

Samuel Issacharoff & Jonathan Nagler,

Protected from Politics: Diminishing

Margins of Electoral Competition in

U.S. Congressional Elections,

eg I e 17

viii

Joint Appendix, League of United Latin

American Citizens v. Perry (LULAC),

Nos. 05-204, 05-254, 05-276, 05-439,

2006 WL 64437 (U.S. Jan. 10. 2006)............. 25, 29

Justin Levitt, Where Are The Lines

Drawn?, All About Redistricting,

https://tinyurl.com/aw3qgn5

(last visited Aug. 10, 2017)................ nbesmiandontaa 20

Jonathan Mattingly et al.,

Quantifying Gerrymandering,

https://tinyurl.com/yc4cvxkg (last

Ce FE: Ne FE ctcciincdisiccessscaciscinstessnennadiiien 31

Michael D. McDonald & Robin E. Best,

Unfair Partisan Gerrymanders in

Politics and Law: A Diagnostic

Applied to Six Cases,

14 Election L.J. 312 (2015)...................... 15, 19, 27

Anthony J. McGann et al.,

Gerrymandering in America

CER TED big Ei 9, 14, 15, 16, 17, 20, 27

Nat’l Conference of State Legislatures,

State Partisan Composition,

https://tinyurl.com/guos34u (last

ee Eis a iheidiendintinictanosintitniinamincnatiaiata 9

Richard G. Niemi, Bernard Grofman,

Carl Carlucci & Thomas Hofeller,

Measuring Compactness and the

Role of a Compactness Standard in a

Test for Partisan and Racial

Gerrymandering,

62 J. of Pol. 1166 (1980).........................

Guillermo Owen & Bernard Grofman,

Optimal Partisan Gerrymandering,

7 Pol. Geography Q. 5 (1988).................

Pew Research Center, Political

Polarization in the American Public,

https://tinyurl.com/p4scahz (last

updated June 12, 2014) ....................06.

Proportional Representation, Encyclope-

dia Britannica (2013 ed.),

https://tinyurl.com/y6welcph.................

Nicholas O. Stephanopoulos & Eric M.

McGhee, Partisan Gerrymandering

and the Efficiency Gap,

82 U. Chi. L. Rev. 831 (2015) ................

Samuel S. H. Wang, Three Practical

Tests for Gerrymandering:

Application to Maryland and

Wisconsin, 16 Election L.J. 367

I idearandinsduisasinacsitetmantenceeeescetcecveconesee

Wis. State Assembly Rules

(Feb. 8, 2017),

https://tinyurl.com/y8rudrg6 .................

Wis. State Senate Rules

(Jan. 17, 2017),

https://tinyurl.com/y8rudrg6 ....................6.:000ee

INTERESTS OF AMICI CURIAE'

Amici are political scientists who specialize in re-

districting, including the statistical methods used to

detect and measure partisan gerrymandering. Amici

have served as expert witnesses and consultants in

redistricting cases on behalf of both states and plain-

tiffs, Republicans and Democrats. They have also

published many peer-reviewed articles on the sub-

ject.?

1 The parties have consented to the filing of this amicus

brief. No counsel for a party authored the brief in whole or in

part. No party, counsel for a party, or any person other than

amici and their counse] made a monetary contribution intended

to fund the preparation or submission of the brief.

2 Professor Grofman’s publications include Bernard

Grofman & Gary King, The Future of Partisan Symmetry as a

Judicial Test for Partisan Gerrymandering after LULAC v.

Perry, 6 Election LJ. 2 (2007); Bernard Grofman, William

Koetzle & Thomas Brunell, An Integrated Perspective on the

Three Potential Sources of Partisan Bias: Malapportionment,

Turnout Differences, and the Geographic Distribution of Party

Vote Shares, 16 Electoral Stud. 457 (1997); Richard G. Niemi,

Bernard Grofman, Carl Carlucci & Thomas Hofeller, Measuring

Compactness and the Role of a Compactness Standard in a Tesi

for Partisan and Racial Gerrvmandering, 52 J. of Pol. 1156

(1990); Guillermo Owen & Bernard Grofman, Optimal Partisan

Gerrymandering, 7 Pol. Geography Q@. 5 (1988); Bernard

Grofman, Michael Migalski & Nichulas Noviello, The “Totality of

Circumstances Test” in Section 2 of the 1982 Extension of the Vot-

ing Rights Act: A Social Science Perspective, 7 L. & Pol'y 199

(1985); Bernard Grofman, Measures of Bias and Proportionality

ut Seats- Votes Relationships, 9 Pol. Methodology 295 (1983).

Professor Gaddie’s publications include Charles S. Bull-

ock, III, Ronald Keith Gaddie, & Justin J. Wert, The Rise and

Amici seek to assist the Court in understanding

recent developments in social science methodologies

for identifying and measuring the extent of partisan

gerrymanders. They do not take a position on

whether, given the particular facts and expert wit-

ness analysis, the district court correctly decided this

case. But amici firmly believe that partisan gerry-

manders are justiciable, and that this Court should

adopt an articulable standard for adjudicating parti-

san gerrymandering claims. Social science tools now

allow courts to diagnose partisan gerrymanders with

accuracy and precision. They also allow courts to dis-

tinguish ordinary, acceptable politicking from con-

duct that rises to the level of unconstitutional

discrimination against voters based on their political

views. If the Court again declines to adopt a standard

for unconstitutional partisan gerrymandering, politi-

cians will have free rein to violate associational and

representational rights.

Amicus Bernard Grofman is the Jack W. Peltason

Chair of Democracy Studies and Professor of Political

Science at the University of California, Irvine. He has

frequently served as an expert witness and consultant

in redistricting cases, including for the State of Ind1-

ana in Davis v. Bandemer, 478 U.S. 109 (1986), and

Fall of the Voting Rights Act (2016); Charles S. Bullock, LIl, &

Ronald Keith Gaddie, The Triumph of Voting Rights in the South

(2009); Ronald Keith Gaddie & Charles S. Bullock, III, From

Ashcroft To Larios: Recent Redistricting Lessons from Georgia,

34 Fordham Urb. L.J. 997 (2007); Ronald Keith Gaddie &

Charles S. Bullock, Lil, Elections to Open Seats In The U.S.

House: Where the Action Is (2000).

for the plaintiffs in Badham v. Eu, 694 F. Supp. 664

(N.D. Cal. 1988), aff'd, 488 U.S. 1024 (1989). He joined

amicus briefs on behalf of neither party in Vieth v. Ju-

belirer, 541 U.S. 267 (2004), and League of United

Latin American Citizens (LULAC) v. Perry, 548 U.S.

399 (2006), arguing that partisan gerrymanders are

justiciable. The Court has previously cited Professor

Grofman’s work (including volumes he edited) in over

a dozen cases,’ and scholars often credit his brief in

LULAC with introducing the Court to the first gener-

ation of social science analysis of partisan asymmetry.

Professor Grofman has also drawn redistricting

plans for federal district courts, non-partisan commis-

sions, and the U.S. Department of Justice-—most re-

cently, as the Special Master appointed by a three-

judge court after it declared Virginia’s Congressional

District 3 unconstitutional. Page v. Va. State Bd. of

Elections, No. 3:13-CV-678, 2015 WL 3604029, at *18

(E.D. Va. June 5, 2015), appeal dismissed sub nom.

Wittman v. Personhuballah, 136 S. Ct. 1732 (2016).

Professor Grofman’s curriculum vitae is available at

https://tinyurl.com/y8ppxmvg.

8 See Ariz. State Legislature v. Ariz. Indep. Redistricting

Comm'n, 135 8S. Ct. 2652 (2015); Shelby County, Alabama v.

Holder, 133 S. Ct. 2612 (2013); LULAC uv. Perry, 548 U.S. 399

(2006); Vieth v. Jubelirer, 541 U.S. 267 (2004); Georgia v. Ash-

croft, 539 U.S. 461 (2003); Abrams v. Johnson, 521 U.S. 74

(1997); Shaw v. Hunt, 517 U.S. 899 (1996); Bush v. Vera, 517

U.S. 952 (1996); Miller v. Johnson, 515 U.S. 900 (1995); Johnson

vu. De Grandy, 512 U.S. 997 (1994); Holder v. Hall, 512 U.S. 874

(1994); Shaw v. Reno, 508 U.S. 630 (1993); Thornburg v. Gingles,

478 U.S. 30 (1986); Davis v. Bandemer, 478 U.S. 109 (1986).

Amicus Ronald Keith Gaddie is the President’s

Associates Presidential Professor and Chair of the De-

partment of Political Science at the University of Ok-

lahoma and an editor of Social Science Quarterly. He

too has served as an expert witness and consultant in

numerous redistricting cases, including for the State

of Texas in LULAC and for the plaintiffs in Cox v. Lar-

ios, 542 U.S. 947 (2004). Most recently, Professor Gad-

die worked as a consultant to the Wisconsin

legislature’s Republican leadership in drafting Act 43,

the map at issue in this case. As the district court ex-

plained, the Republican Caucus’s attorneys hired Pro-

fessor Gaddie to assess, among other things, the

expected partisan impact of the proposed maps. J.S.

App. 12a-14a, 4la-42a, 127a, 13la, 135a, 138a-39a.

Professor Gaddie also testified in defense of the map

in the prior Voting Rights Act challenge, Baldus v.

Members of Wisconsin Government Accountability

Board, 849 F. Supp. 2d 840 (E.D. Wisc. 2012). He did

not, however, defend the map’s constitutionality in

this litigation. He has always believed that partisan

gerrymanders are justiciable. His curriculum vitae is

available at https://tinyurl.com/ya62povt.

INTRODUCTION AND SUMMARY OF

ARGUMENT

Modern, computer-driven redistricting now al-

lows the political party in power to craft extremely so-

phisticated partisan gerrymanders. With vastly

improved computer speed, memory, and storage, map

drawers can design district lines so precisely that

they simultaneously maximize their party’s gains and

eliminate most competitive districts—ensuring that

the party in power enjoys an electoral advantage that

endures throughout the following decade, irrespective

of voters’ subsequent choices.

Left unchecked, partisan gerrymandering funda-

mentally undermines our democracy. It is a basic

tenet of fair elections that the parties must play by

the same rules. But a partisan gerrymander violates

that core principle: Under a successful partisan ger-

rymander, one party needs fewer votes to win repre-

sentation than the other party. A _ partisan

gerrymander places unequal burdens on voters’ op-

portunity to elect their representatives, based on the

party with which they associate. And where the par-

tisan gerrymander is unresponsive to electoral shifts,

only the courts can provide a remedy.

This Court should hold that partisan gerryman-

dering claims are justiciable. To be precise, partisan

gerrymandering occurs when a districting plan penal-

izes the minority in its ability to translate its voting

support into seats compared to what might be ex-

pected from a plan drawn on the basis of neutral prin-

ciples. But not all partisan gerrymanders are

unconstitutional. The Court should adopt a test for

unconstitutional partisan gerrymandering that re-

quires a showing of three specific elements: partisan

asymmetry, lack of responsiveness, and causation.

The first element, partisan asymmetry, is based

on the idea that a citizen’s representational rights

must not depend on the party with which he chooses

to affiliate. Unlike a claim that the plaintiff is entitled

to a specified number of seats, an asymmetry stand-

ard requires only that the parties and their support-

ers receive equal treatment—that they have like

opportunity to translate their votes into representa-

tion. Thus, if Party A would garner, say, 60% of the

seats when it wins 53% of the votes, Party B should

also garner about 60% of the seats when it wins 53%

of the votes. If it would not, partisan asymmetry is

present. The second element, lack of responsiveness,

screens out cases where the political process can pro-

vide a remedy. It examines whether a map is respon-

sive to shifts in voters’ allegiances, such that any

disparate effect on voters is unlikely to persist

throughout the decade following redistricting. If a

map is responsive, then when voters change their al-

legiances, their representation also changes, making

judicial intervention unnecessary. If a map is not re-

sponsive, the courts may step in. The third element,

causation, requires that, to be actionable, a disparate

effect on voters must be the result of invidious, inten-

tional discrimination against disfavored voters—and

not merely the natural byproduct of ordinary district-

ing practices or chance.‘

These three elements are derived from the Court’s

Equal Protection and First Amendment jurispru-

dence, and the social sciences offer tools for measur-

ing each. Because each of these elements reflects a

different concept, it is important to recognize that no

one number tells it all. Rather, the Court should adopt

a test for partisan gerrymandering that makes each

4 Intent can also be proven through non-statistical evi-

dence—for example, legislators’ own statements about their mo-

tives; departures from traditional districting criteria, such as

irregular-shaped districts; and process considerations like se-

crecy, limited debate, or party-line voting in the enactment of the

map. We focus here on the applicable social science evidence.

of these three elements a necessary, but not sufficient,

condition of a claim.

In none of the Court’s prior partisan gerryman-

dering cases did the plaintiffs propose such a test,

much less offer evidence of all three elements. And the

statistical tools for detecting and measuring partisan

gerrymanders have improved greatly since the Court

last considered partisan gerrymandering in LULAC.

Courts—assisted by competent experts—can now re-

liably and accurately identify and measure the impact

of partisan gerrymanders, including determining

whether invidious discrimination is the cause of any

disparate burden on one political party, or whether

any disadvantage results instead from permissible,

neutral factors or random chance. The courts can, and

should, play a role in policing improper partisan ger-

rymanders.

ARGUMENT

I. Courts Must Provide A Check On Egregious

Partisan Gerrymandering.

Invidious partisan gerrymandering occurs when a

political party intentionally redraws legislative dis-

trict lines to give itself a durable electoral advantage

over the party out of power—usually by “packing” vot-

ers who affiliate with the opposing party into a few

safe districts, or by “cracking” them across multiple

districts to dilute their voting power. See Bandemer,

478 U.S. at 117 n.6 (explaining “the familiar tech-

niques of political gerrymandering”). In so doing, a

partisan gerrymander discriminates against voters in

their representational rights because of their views

and political associations in a way that cannot realis-

tically be ameliorated through the ordinary electoral

process. See Vieth, 541 U.S. at 314 (opinion of Ken-

nedy, J.) (“First Amendment concerns arise where a

State enacts a law that has the purpose and effect of

subjecting a group of voters or their party to disfa-

vored treatment by reason of their views. In the con-

text of partisan gerrymandering, that means... where

an apportionment has the purpose and effect of bur-

dening a group of voters’ representational rights.”)

(opinion of Kennedy, J.); Bandemer, 478 U.S. at 124

(“[E]ach political group in a State should have the

same chance to elect representatives of its choice as

any other political group.”).

This discrimination in representational rights

has real-world consequences. A voter who supports a

disfavored party is denied an equal opportunity to use

her vote to affect the representation of her district, as

well as the partisan composition of the legislature as

a whole. And the composition of the legislature carries

high stakes. In states using a caucus system, the

party holding the majority of a chamber’s seats con-

trols all aspects of the legislative agenda—from what

bills will see the light of day to the budget, procedural

rules, committee assignments, and so forth. See, e.g.,

J.S. App. 7a-9a, 106a; Wis. State Assembly Rules

(Feb. 8, 2017); Wis. State Senate Rules (Wan. 17,

2017). Available at https://tinyurl.com/y8rudrg6. In-

deed, even in states where the majority party has less

formal agenda-setting power, the partisan makeup of

the legislature directly impacts the legislation that is

introduced, debated, and passed.

There is compelling evidence that the 2010 redis-

tricting cycle yielded partisan gerrymandering of a

magnitude that is qualitatively and quantitatively

different from what we have seen in the past—as

much as three times more partisan bias than in the

2000 redistricting cycle—even when controlling for

residential patterns of voters and demographic

change. Anthony J. McGann et al., Gerrymandering

in America 4-5, 97-98 (2016). Indeed, there were

strong increases in bias even where the same party

controlled both the 2000 and 2010 redistricting pro-

cesses. Id. at 174. This increase in the aggressiveness

of partisan gerrymanders may be driven in part by

the fact that, as a result of the Court’s “signal{] in Vi-

eth v. Jubelirer (2004) that it would not intervene ...|,]

state legislatures did not have to worry about the

threat of legal oversight and pushed partisan ad-

vantage to its limits” during the 2010 cycle. Id. Absent

a judicial check, the level of egregious partisan gerry-

mandering may worsen still in 2020 because of a

marked increase in the number of legislatures under

unified partisan control. See Nat’] Conference of State

Legislatures, State Partisan Composition, https://ti-

nyurl.com/guos34u (last updated Aug. 1, 2017).

Whether courts should police egregious partisan

gerrymanders is not a matter of one’s political lean-

ings. While evidence suggests that at a national level,

the net benefits of partisan gerrymandering currently

accrue to Republicans, in the past, the benefits have

accrued to Democrats. McGann et al., supra, at 71-72,

88. Whichever party is in power has strong incentives

to change the map to keep itself there. In either case,

it is the voters who lose: Their associational and rep-

resentational rights are undermined based upon their

political views, and incumbents are entrenched in of-

fice without regard to changes in voter preferences.

The courts must serve as a neutral check. If the

Court again declines to adopt a standard for unconsti-

tutional partisan gerrymandering, politicians will

have free rein to wield the technological advances we

discuss below to craft ever more egregious partisan

gerrymanders. Continued judicial abdication would

ensure only that our representatives are selected by

the self-dealing maps they enact, rather than elected

by the people they ostensibly serve—freezing into

place for a decade electoral advantages that are, for

all practical purposes, impervious to changes by the

electorate.

Il. A Justiciable Partisan Gerrymandering

Claim Requires Proof Of Partisan

Asymmetry, Lack Of Responsiveness, And

Causation.

Social science now provides tools for determining

whether voters have been subjected to durable dispar-

ate treatment—as well as for measuring the precise

magnitude of any such disparity and for ruling out

neutral causes. These tools enable courts to differen-

tiate between disparate burdens on representational

rights that are merely incidental to ordinary district-

ing processes, and those that are the result of inten-

tional discrimination against disfavored voters.

There is consensus among social scientists that

three discrete concepts are critical to detecting and

measuring the extent of an unconstitutional partisan

gerrymander: (1) partisan asymmetry, (2) lack of re-

sponsiveness of electoral outcomes to changes in voter

decisions, and (3) causation. The Court should adopt

a test for unconstitutional partisan gerrymanders

that makes proof of each of these elements necessary

for a claim. Together, these elements—which, alt-

hough independently derived, largely parallel the

standard proposed by the plaintiffs here—are key to

demonstrating that voters have suffered disparate

and durable burdens on their representational rights

because of their political views and associations. They

also provide evidence as to whether any differential

treatment is intentional or instead is the result of

other, neutral factors.

This test is not based on an abstract notion of fair-

ness akin to a requirement that seat share equal the

party’s share of the overall vote. It is a standard of

neutral treatment of the parties in allocating repre-

sentational rights. And the burden on voters is meas-

ured relative to the baseline created by neutral

factors: single-member, winner-take-all elections (the

norm in the United States); compliance with federal

constitutional requirements and the Voting Rights

Act; the actual residential patterns of the electorate;

map-drawing practicalities like the need for contigu-

ous and compact districts; and the role of random

chance. The test recognizes that map drawing inevi-

tably has some political fallout, while giving courts a

means to distinguish and identify those egregious

partisan gerrymanders that go above and beyond to

invidiously target opposition voters for unequal treat-

ment.

The first element, partisan asymmetry, considers

whether and to what degree voters’ representational

rights have been burdened. The second, lack of re-

sponsiveness—also called “durability”’—considers

whether the ordinary political process is able to pro-

vide a remedy. And the third, causation, ensures that

only invidious, intentional discrimination is actiona-

ble, as distinct from disparate effects that are merely

the result of neutral factors or chance. No one factor

is dispositive. Rather, each of these three discrete el-

ements—partisan asymmetry, lack of responsiveness,

and causation—must be assessed separately and

should be deemed a necessary, but not sufficient, con-

dition of a partisan gerrymandering claim.

A. Partisan asymmetry means there is a

disparate impact on voters based on

political affiliation.

The first element, partisan asymmetry, speaks to

whether there has been a clear and severe disparate

impact on a political party and its supporters. It asks

whether the map treats similarly situated parties

equally: whether both parties receive like opportunity

to capture a given number of legislative seats if they

receive a comparable share of the statewide vote.

For example, imagine that the “Democratic Party

receives an average of 55% of the vote totals in a

state’s legislative district elections and, because of the

way the district lines were drawn, it wins 70% of the

legislative seats in that state.” Bernard Grofman &

Gary King, The Future of Partisan Symmetry as a Ju-

dicial Test for Partisan Gerrymandering after LULAC

v. Perry, 6 Election L.J. 2, 8 (2007). This “one piece of

evidence alone” says nothing about whether any vot-

ers have been treated differently based on their polit-

ical views. Id. That turns on whether the result would

be different were the shoe on the other foot: If the Re-

publican Party would also have received 70% of the

seats in an election in which it garnered an average

of 55% of the vote, then there is no disparate treat-

ment. Id.

Critically, as the foregoing example indicates, a

symmetry standard is not equivalent to a proportion-

ality standard, which this Court has rightly rejected.

In a system of proportional representation (used in

many European countries), seats are awarded in pro-

portion to overall vote share—i.e., 30% of the

statewide votes would garner about 30% of the legis-

lative seats. Proportional Representation, Encyclope-

dia Britannica (2013 ed.), ##$.available= at

https://tinyurl.com/y6welcph. Supreme Court prece-

dents “clearly foreclose any claim that the Constitu-

tion requires proportional representation.”

Bandemer, 478 U.S. at 130 (opinion of White, J.).

Nor does mere disproportionality evidence a par-

tisan gerrymander. The political science is clear: Win-

ner-take-all, single-member district elections—

elections in which a plurality of the votes wins the dis-

trict’s seat—do not produce proportionate results, be-

cause “in practice they normally give a ‘bonus’ of

varying sizes (above proportionality) in seats to the

party that wins a majority of the votes across a state.”

See Grofman & King, The Future of Partisan Sym-

metry, supra, at 9; see also, e.g., Samuel S. H. Wang,

Three Practical Tests for Gerrymandering: Applica-

tion to Maryland and Wisconsin, 16 Election L.J. 367,

368, 374 (2016). Thus, it is generally not possible to

directly infer asymmetry from disproportionality. See

McGann et al., supra, at 65-66 (“[A symmetry stand-

ard] does not require proportionality but only that the

disproportionality be the same for both parties.”).

Rather than embodying a particular political the-

ory, partisan symmetry requires only that if we were

to “switch the names of the parties that received par-

ticular vote outcomes, the seat outcomes would also

switch.” Grofman & King, The Future of Partisan

Symmetry, supra, at 8. “[I]n other words[,]” it requires

“that outcomes not depend on party names.” Jd. And

measures of partisan asymmetry show not only

whether a map provides an advantage to one party

over another, but also the degree of the advantage.

The scholarly literature has uniformly supported

partisan asymmetry as the definition of disparate

partisan impact in electoral systems since at least the

late 1980s. See id. at 6 & nn.29-30 (canvassing publi-

cations on the subject). But as explained below (§ IID),

until now, the concept has never been squarely pre-

sented to this Court.

B. Lack of responsiveness means the

ordinary political process cannot

provide a remedy.

The second necessary element derived from social

science is lack of responsiveness. While asymmetry

shows a disparate effect on voters’ representational

rights, that alone is not enough to demonstrate an im-

proper gerrymander. If the party out of power can al-

ter its fate by persuading voters to support it in the

next election, then there is no need for courts to inter-

vene. Rather, ordinary politics remain responsive to

voters’ preferences, and if citizens do not like the pol-

icles promulgated by their representatives (including

the district maps they enact), they can vote them out

of office. See Michael D. McDonald & Robin E. Best,

Unfair Partisan Gerrymanders in Politics and Law: A

Diagnostic Applied to Six Cases, 14 Election L.J. 312,

319 (2015) (arguing that the Court “entered the met-

aphorical political thicket in the 1960s on the ques-

tion of malapportionment” due to “the practical

problem ... that popular majorities had no political

means to correct the offense”); Nicholas O. Stepha-

nopoulos & Eric M. McGhee, Partisan Gerrymander-

ing and the Efficiency Gap, 82 U. Chi. L. Rev. 831, 865

(2015) (“So long as certain plans would remain unbal-

anced over an array of potential outcomes ... the case

for judicial intervention is unaffected.”).

Moreover, the magnitude of partisan asymmetry

and its expected duration can be unrelated. McGann

et al., supra, at 65 (“These two qualities [of asym-

metry and responsiveness] are independent.”). In

principle, even large-scale disparities in treatment of

the parties can be fleeting. A constitutional standard

for partisan gerrymanders should accordingly require

a separate assessment of electoral responsiveness,

sometimes called “durability.”

Electoral responsiveness describes whether and

how representation changes when voters’ preferences

change. Based on historical data—how much voters’

preferences swung in prior elections—experts can

identify the full range of realistically possible election

outcomes (vote shares) and then determine how many

legislative seats, if any, would change hands in re-

sponse to a comparable change in voters’ choices. The

number of competitive districts also provides evidence

of the map’s responsiveness.

If a map is not responsive, that means that when

voters change their preferences and shift their alle-

giances from one party to another, their representa-

tion remains unlikely to change—showing that the

politicians have chosen the voters, and not the other

way around. In that circumstance, we can expect par-

tisan asymmetry to endure regardless of the outcome

of future elections. Conversely, high responsiveness

suggests that the disparate effect on voters may not

be long-lasting.

Measuring responsiveness will also detect a so-

called “dummymander.” Bernard Grofman & Thomas

L. Brunell, The Art of the Dummymander: The Impact

of Recent Redistrictings on the Partisan Makeup of

Southern House Seats, Redistricting in the New Mil-

lennium 183, 184 (Peter Galderisi ed., 2005). As Jus-

tice O'Connor noted in Bandemer, some

gerrymanders could be “self-limiting,” if map drawers

crack voters across multiple districts to create mar-

gins of victory so thin that they evaporate in future

elections. Bandemer, 478 U.S. at 152 (O’Connor, J.,

concurring). But dummymanders can occur only when

there are a number of competitive districts in a map.

And there is empirical evidence that dummymanders

are rare. See McGann et al., supra, at 226 (“A second

myth we have debunked is that partisan gerryman-

dering is self-limiting”).5 In any event, assessing re-

sponsiveness “allows us to distinguish those cases in

which a gerrymandering might have been attempted

but was not very well done from those cases in which

the partisan bias imposed by gerrymandering is ex-

pected to be both substantial and long-lasting.”

Grofman & King, The Future of Partisan Symmetry,

supra, at 13.

5 There are two clear explanations for why dummymanders

are so uncommon: First, the newest, computer-driven redistrict-

ing now allows map drawers to make very precise refinements

to district lines down to the census-block level. With this sophis-

ticated new technology, map drawers can tashion maps that

eliminate meaningful competition for most districts. See

McGann et al., supra, at 87 (“[A]Jrmed with modern geographical

information system software and an absence of judicial con-

straints, it is possible to engineer so much advantage that [a map

can] satisfy both ... goals” of “seat maximization and incumbent

protection.”). Thus, generally speaking, gerrymandered victory

margins are no longer so thin that they risk disappearing. See

Samuel Issacharoff & Jonathan Nagler, Protected from Politics:

Diminishing Margins of Electoral Competition in U.S. Congres-

sional Elections, 68 Ohio St. L.J. 1121, 1122 (2007) (“[D]espite

relative overall national parity between the parties in the post-

War period, the districts held by each party tend to be more

firmly in their control than ever before.”). Second, political po-

larization of the electorate is increasing. See Pew Research Cen-

ter, Political Polarization in the American Public, available at

https://tinyurl.com/p4scahz (last updated June 12, 2014) (“Re-

publicans and Democrats are more divided along ideological

lines—and partisan antipathy is deeper and more extensive—

than at any point in the last two decades.”). With fewer swing

voters, there is less risk of a victory margin eroding over time.

Requiring that plaintiffs demonstrate that a dis-

parate partisan impact will be durable throughout the

decade following redistricting—that the map is not re-

sponsive to voters—ensures that courts do not inter-

vene in the political process when it is functioning

properly. If the map does not persistently obstruct

competition, the voters’ remedy lies at the polls, not

in the courts.®

C. Causation means that the partisan

asymmetry is a result of invidious

discrimination, not neutral factors or

chance.

Assessing partisan asymmetry and responsive-

ness is still not enough. There is a consensus among

social scientists that to determine whether invidious

discrimination is the cause of a disparate burden on

voters, it is mecessary to rule out other potential

causes—to assess whether the partisan effects of a

plan are attributable, for example, to neutral princi-

ples, voters’ residential patterns, or sheer random

6 Conversely, that responsiveness is low is not, by itself,

enough to establish an unconstitutional partisan gerrymander.

For example, if both parties agree to apportion single-member

districts in proportion to their respective vote shares, that would

be “effectively synonymous with requiring low levels of electoral

responsiveness.” Grofman & King, The Future of Partisan Sym-

metry, supra, at 9. Yet there is no need for judicial intervention

when legislatures choose to apportion the state proportionately.

Gaffney v. Cummings, 412 U.S. 735, 754 (1973) (“[Jjudicial in-

terest should be at its lowest ebb when a State purports fairly to

allocate political power to the parties in accordance with their

voting strength[.}”). As with asymmetry and causation, low re-

sponsiveness is a necessary but not sufficient condition for a con-

stitutional claim.

chance. See, e.g., Wang, Three Practical Tests, supra,

at 374 (“[A] standard for partisan gerrymandering re-

quires a method for determining whether a [claimed

disparity] could have arisen as part of normal varia-

tion in districting as practiced across the United

States.”); McDonald & Best, supra, at 317 (“[I])n order

to distinguish unintentional from intentional gerry-

manders, a benchmark of what naturally would result

from any neutral line drawing has to be estab-

lished.”); Jowei Chen & Jonathan Rodden, Cutting

Through the Thicket: Redistricting Simulations and

the Detection of Partisan Gerrymanders, 14 Election

L.J. 312, 332 (2015) (“[Plartisan asymmetry in the

transformation of votes to seats could happen for sev-

eral reasons that cannot be traced to partisan manip-

ulation ....”). That is, we must compare the map’s

disparate effects against a neutral baseline.

As the Court has noted, advantages to one party

may occur due to a variety of neutral factors. See, e.g.,

Vieth, 541 U.S. at 289-90 (plurality); id. at 308-09

(Kennedy, J., concurring). For example, map drawers

must comply with the Constitution’s “one-person, one-

vote” and non-discrimination requirements. They also

must comply with the Voting Rights Act. See Charles

S. Bullock, III, & Ronald Keith Gaddie, The Triumph

of Voting Rights in the South 343 (2009) (discussing

partisan alignment of groups protected by Voting

Rights Act). And many states’ laws also require map

drawers to take into account certain traditional dis-

tricting criteria. Almost every state, for example, re-

quires districts to be contiguous. Most also require

compact districts that do not split political subdivi-

sions across districts. And a handful require the

preservation of communities of interest—groups of

people with a common interest like race or ethnicity.

See, e.g., Justin Levitt, Where Are The Lines Drawn?,

All About Redistricting, https://tinyurl.com/aw3qgn5

(last visited Aug. 10, 2017) (collecting current, state-

by-state legal requirements for redistricting); see also

Bernard Grofman, Criteria for Districting: A Social

Science Perspective, 33 UCLA L. Rev. 77 (1985) (Table

3) (collecting state-by-state requirements for 1980s

round of redistricting).

Compliance with these neutral criteria may lead

to inadvertent advantages to one party. Similarly,

there is some evidence that “political groups that tend

to cluster (as is the case with Democratic voters in cit-

ies) [clould be systematically affected by what might

be called a ‘natural’ packing effect,” Vieth, 541 U.S. at

290 (plurality)—although new empirical evidence in-

dicates that this effect has been overstated. McGann

et al., supra, at 135 (“[G]jeographic and demographic

constraints (such as the urban concentration of Dem-

ocratic voters, the requirement to draw majority-mi-

nority districts, and the geographic sorting of voters)

cannot account for the level of partisan bias we ob-

serve and certainly cannot account for the increase in

bias we observe between the 2000 and 2010 district-

ing rounds.”). Partisan asymmetry could also poten-

tially occur by random chance in the map-drawing

process.

Partisan asymmetry that is merely a side effect of

indisputably legitimate objectives within the redis-

tricting process or that is naturally occurring does not

evidence actionable invidious discrimination. Any

constitutional test for partisan gerrymandering will

thus have to rule out these causes of asymmetry and

isolate the degree of asymmetry that is “unrelated to

the [legitimate] aims of apportionment,” or to residen-

tial patterns or chance. Vieth, 541 U.S. at 313 (Ken-

nedy, J., concurring).

As explained below (§ III), there are now ex-

tremely sophisticated and accurate methods of ruling

out neutral factors as the source of partisan asym-

metry. These tools enable experts to identify the pre-

cise quantum of disparate treatment that is “man-

made”—the product of deliberate efforts of the party

in power to penalize the opposition—as distinct from

the level of disparity that may be produced by the ef-

fects of neutral districting priorities, voters’ residen-

tial patterns, or chance. See, e.g., Jowei Chen &

Jonathan Rodden, Cutting Through the Thicket: Re-

districting Simulations and the Detection of Partisan

Gerrymanders, 14 Election L.J. 312 (2015).

kkk

When partisan asymmetry, lack of responsive-

ness, and causation are each shown, we are able to

establish the existence of discrimination against vot-

ers based on their political views and associations

that is unlikely to be remedied by the political pro-

cess. Beyond that, whether courts should nonetheless

tolerate some degree of discrimination before they

will intercede is a question for judges, not social sci-

entists. The question of “how much partisan domi-

nance is too much,” LULAC, 548 U.S. at 420 (opinion

of Kennedy, J.), is fundamentally a legal one for

courts to decide.’

Ill. The Court Has Never Before Confronted

Reliable Evidence Of These Three Discrete

Elements.

Social science now offers straightforward and

manageable ways to prove (or disprove) partisan

asymmetry, lack of responsiveness, and causation.

But that was not always true. The analytical tools for

evaluating each of these three elements have dramat-

ically improved since the Court last considered the

justiciability of partisan gerrymandering in LULAC.

It is thus unsurprising that this is the first case before

this Court in which the plaintiffs offered evidence of

each of the three necessary elements. See, e.g., J.S.

’ The available social science tools are now well suited to

analyzing the kind of threshold requirements that the Court has

adopted in other election-law contexts. For example, the Court

could require the plaintiffs to establish that at least one seat now

lost to partisan gerrymandering could be gained in a neutral

plan. This is feasible because most measures of asymmetry can

be translated into a percentage of the seats in a plan affected.

Cf. Bartlett v. Strickland, 556 U.S. 1, 26 (2009) (adopting, in Vot-

ing Rights Act § 2 case, threshold requirement that plaintiffs

demonstrate a “geographically compact group of minority voters

[that] could form a majority in a single-member district”). Alter-

natively, the Court could set a threshold level of partisan asym-

metry that triggers judicial scrutiny, using historical data to

identify the amount of asymmetry that is atypical or egregious.

Cf. Brown v. Thomson, 462 U.S. 836, 842 (1983) (“Our [one-per-

son-one-vote] decisions have estahlished ... that a [state legisla-

tive] apportionment plan with a maximum population deviation

under 10% falls within this category of minor deviations [that

are not actionable.}”).

App. 146a-66a, 173a-74a (asymmetry and responsive-

ness, i.e., durability), 180a-8la, 19la-196a, 197a

n.350, 200a-12a (causation, i.e., absence of justifica-

tion).

A. Bandemer, Vieth, and LULAC did not

consider evidence of partisan

asymmetry, lack of responsiveness, and

causation.

In the course of rejecting the plaintiffs’ claims in

Bandemer, Vieth, and LULAC, the Court hinted that

partisan asymmetry, lack of responsiveness, and cau-

sation are important to a justiciable partisan gerry-

mandering claim. See LULAC, 548 U.S. at 418

(holding that “unconstitutional acts of partisan gerry-

mandering must do what appellants’ sole-motivation

theory disavows: show a burden, as measured by a re-

liable standard, on the complainants’ representa-

tional rights”); Vieth, 541 U.S. at 289-90 (plurality)

(holding that plaintiffs failed to establish a standard

under which they were entitled to a majority of the

seats, and that they failed to rule out “natural” causes

of packing); Bandemer, 478 U.S. at 129-130, 140

(holding that plaintiffs’ claims failed because propor-

tionality is not required and because “more than a

showing of possibly transitory results” is required).

But in none of those cases did the plaintiffs (or the

Justices) propose a test based on these elements, and

the plaintiffs never provided evidence of these ele-

ments to the Court. Indeed, the first and only time the

Court addressed partisan asymmetry was in LULAC,

where only an amicus brief (which Professor Grofman

joined), and not the parties, discussed the concept.

Contrary to the Whitford defendants’ contention

that the evidence in this case is equivalent to that re-

jected in Bandemer (Brief for Appellants 39), the pri-

mary evidence in Bandemer was that a single election

had yielded slightly disproportionate results. 478 U.S.

at 134 (plurality). The Bandemer plaintiffs offered no

evidence of partisan asymmetry, lack of responsive-

ness, or causation. Instead of partisan asymmetry,

they offered proportionality. But as Professor

Grofman-——Indiana’s expert witness in that case—ex-

plained, it is “totally fallacious ... that a discrepancy

between vote share and seat share of more than a few

percentage points is proof of intentional gerryman-

dering.” Grofman, Criteria for Districting, supra, at

120. Nor did the plaintiffs there offer any evidence of

lack of responsiveness, leaving unrebutted the State’s

contention that if the plaintiffs won even an “addi-

tional few percentage points ..., they would have ob-

tained a majority ... in both houses.” Bandemer, 478

U.S. at 135 (plurality). Finally, plaintiffs failed to

prove causation because their test left unaddressed

discrepancies in treatment caused merely by “natural

advantages.” Grofman, Criteria for Districting, supra,

at 120.

In Vieth, the plaintiffs took a somewhat different

tack. They argued for a two-pronged test: (1) a pre-

dominant intent to achieve partisan advantage,

shown through the subordination of neutral and legit-

imate criteria (i.e., intent); and (2) a “totality of the

circumstances” determination that the map could

“thwart the plaintiffs’ ability to translate a majority

of votes into a majority of seats,” (i.e., effect). 541 U.S.

at 284-87 (plurality).

The effects prong of this test focused on the wrong

criteria: It claimed that a party that won the majority

of votes was entitled to a majority of seats, without

establishing any differential treatment of voters

based on their political views and associations. Spe-

cifically, because the case was decided on a motion to

dismiss, and because no election had taken place un-

der the challenged plan, the plaintiffs’ claim of ad-

verse effects rested solely on an allegation that, in the

future, they would be deprived of a majority of Penn-

sylvania’s congressional seats, despite achieving a

majority of the statewide vote. Jd. at 272-73, 287. The

plurality noted that this claim reduced to a claim of

proportional representation, similar to the propor-

tionality test urged in Bandemer. Id. at 288. And of

course, there was no evidence of partisan asymmetry,

responsiveness, or causation.

In LULAC, the district court heard limited expert

evidence regarding partisan asymmetry and respon-

siveness, including testimony from Professor Gad-

die—namely, a measure of “partisan bias” that

examined how many seats each party would win if,

hypothetically, each obtained 50% of the statewide

vote. 548 U.S. at 466-68 (Stevens, J., concurring in

part and dissenting in part). See also J.A., League of

United Latin American Citizens v. Perry (LULAC),

Nos. 05-204, 05-254, 05-276, 05-439 2006 WL 64437,

at *36-37 (U.S. Jan. 10. 2006) (report of Professor

John R. Alford, expert for plaintiffs); id. at *216 (re-

port of Professor Gaddie, expert for the State).

But, plaintiffs abandoned this evidence by the

time they got to this Court. Instead, their theory of

Contrary to the Whitford defendants’ contention

that the evidence in this case is equivalent to that re-

jected in Bandemer (Brief for Appellants 39), the pri-

mary evidence in Bandemer was that a single election

had yielded slightly disproportionate results. 478 U.S.

at 134 (plurality). The Bandemer plaintiffs offered no

evidence of partisan asymmetry, lack of responsive-

ness, or causation. Instead of partisan asymmetry,

they offered proportionality. But as Professor

Grofman—-Indiana’s expert witness in that case—ex-

plained, it is “totally fallacious ... that a discrepancy

between vote share and seat share of more than a few

percentage points is proof of intentional gerryman-

dering.” Grofman, Criteria for Districting, supra, at

120. Nor did the plaintiffs there offer any evidence of

lack of responsiveness, leaving unrebutted the State’s

contention that if the plaintiffs won even an “addi-

tional few percentage points ..., they would have ob-

tained a majority ... in both houses.” Bandemer, 478

U.S. at 135 (plurality). Finally, plaintiffs failed to

prove causation because their test left unaddressed

discrepancies in treatment caused merely by “natural

advantages.” Grofman, Criteria for Districting, supra,

at 120.

In Vieth, the plaintiffs took a somewhat different

tack. They argued for a two-pronged test: (1) a pre-

dominant intent to achieve partisan advantage,

shown through the subordination of neutral and legit-

imate criteria (i.e., intent); and (2) a “totality of the

circumstances” determination that the map could

“thwart the plaintiffs’ ability to translate a majority

of votes into a majority of seats,” (i.e., effect). 541 U.S.

at 284-87 (plurality).

The effects prong of this test focused on the wrong

criteria: It claimed that a party that won the majority

of votes was entitled to a majority of seats, without

establishing any differential treatment of voters

based on their political views and associations. Spe-

cifically, because the case was decided on a motion to

dismiss, and because no election had taken place un-

der the challenged plan, the plaintiffs’ claim of ad-

verse effects rested solely on an allegation that, in the

future, they would be deprived of a majority of Penn-

sylvania’s congressional seats, despite achieving a

majority of the statewide vote. /d. at 272-73, 287. The

plurality noted that this claim reduced to a claim of

proportional representation, similar to the propor-

tionality test urged in Bandemer. Id. at 288. And of

course, there was no evidence of partisan asymmetry,

responsiveness, or causation.

In LULAC, the district court heard limited expert

evidence regarding partisan asymmetry and respon-

siveness, including testimony from Professor Gad-

die—namely, a measure of “partisan bias” that

examined how many seats each party would win if,

hypothetically, each obtained 50% of the statewide

vote. 548 U.S. at 466-68 (Stevens, J., concurring in

part and dissenting in part). See also J.A., League of

United Latin American Citizens v. Perry (LULAC),

Nos. 05-204, 05-254, 05-276, 05-439 2006 WL 64437,

at *36-37 (U.S. Jan. 10. 2006) (report of Professor

John R. Alford, expert for plaintiffs); id. at *216 (re-

port of Professor Gaddie, expert for the State).

But, plaintiffs abandoned this evidence by the

time they got to this Court. Instead, their theory of

the case was that the sole motive for the Texas legis-

lature’s decision to engage in mid-decennial redis-

tricting was to reap partisan advantage. Jd. at 416-17

(opinion of Kennedy, J.). In other words, their theory

depended only on intent. In fact, they argued that

“courts need not inquire about, nor parties prove, the

discriminatory effects of partisan gerrymandering.”

Id. at 417 (emphasis added). Professor Grofman

raised the concept of partisan asymmetry as relevant

to discriminatory effect in his amicus brief, but the

parties did not squarely present the issue. See Amici

Br. of Prof. Gary King et al., League of United Latin

American Citizens v. Perry (LULAC), Nos. 5-204, 5-

254, 5-276, 5-439, 2006 WL 53994 (U.S., Jan. 10,

2006).

B. The analytical tools for evaluating these

three elements have dramatically

improved since Bandemer, Vieth, and

LULAC.

The analytical tools for evaluating partisan asym-

metry, lack of responsiveness, and causation have

also dramatically improved since Bandemer, Vieth,

and LULAC.

In LULAC, Justice Kennedy expressed concern

that the measure of “partisan bias” that examined

how many seats each party would win if it obtained

50% of the statewide vote relied on “a hypothetical

state of affairs.” Id. at 420 (opinion of Kennedy, J.).

The test of partisan asymmetry that we propose does

not involve predictions about who will win future elec-

tions. Instead, if the “Democratic Party receives an

average of 55% of the vote totals in a state’s legislative

district elections and, because of the way the district

lines were drawn, it wins 70% of the legislative seats

in that state,” our test asks whether the result would

be different were the shoe on the other foot: If the Re-

publican Party would also have received about 70% of

the seats in an election in which it garnered an aver-

age of 55% of the vote. Supra, at 12-13. In any event,

in cases like this one where multiple elections have

occurred under the challenged plan, the accuracy of

the seats-votes graph used to calculate the magnitude

of any partisan asymmetry can be directly confirmed.

Moreover, new measures of asymmetry developed

after LULAC rely on no “hypothetical” counterfactual

at all. For example, the average-median difference is

“a simple measure of asymmetry or skewness ...

[with] well-defined mathematical properties.” Wang,

Three Practical Tests, supra, at 372. The average-me-

dian difference compares each party’s actual vote

share in its median district to its average actual vote

share across all districts. If the party’s median vote

share is significantly lower than its average vote

share, partisan asymmetry is at work. This is because

“(bly packing opposing voters into a small number of

districts, the gerrymandering party holds down the

targeted party’s vote shares in many districts, which

depresses the target party’s median vote share, even

while its average (mean) vote share is unchanged.”

Amicus Br. of Samuel S. Wang, Harris v. Ariz. Indep.

Redistricting Comm'n, No. 14-232, 2015 WL 6774017,

at *4 (U.S. Nov. 2, 2015). The average-median differ-

ence is also highly manageable for courts: “[i]t focuses

on two observable numerical facts’—the mean and

the median-—“and subtracts one from the other.”

McDonald & Best, supra, at 316. This is the first case

in which the plaintiffs have presented evidence of the

average-median difference. See Mot. to Affirm at 12

n.4, 21 n.8.

The plaintiffs here have also made use of another,

easy-to-calculate measure that analyzes actual elec-

tion results—the efficiency gap. See J.S. App. 159a-

66a. The efficiency gap is intended to address parti-

san asymmetry, in that it compares how many votes

each party respectively “wasted” in a given election—

the votes each party received that did not contribute

to it winning an additional seat. Stephanopoulos &

McGhee, supra, at 849-50.8 Like the average-median

difference, the efficiency gap is a social science tool

never before presented to the Court.

In LULAC, Justice Kennedy also explained that

“asymmetry alone is not a reliable measure.” 548 U.S.

at 420 (opinion of Kennedy, J.) (emphasis added). As

explained in §II, we agree. Although Professor

Grofman’s amicus brief in LULAC focused on the rel-

evance of asymmetry to partisan gerrymandering

* In this case, the plaintiffs also used the efficiency gap as a

measure of responsiveness. They presented evidence regarding

Act 43 efficiency gap in the elections following adoption of the

map. J.S. App. 50a. They also presented a historical] analysis

suggesting that when a map exhibits an efficiency gap of a suffi-

ciently large magnitude in the first election following its adop-

tion (7% or more), the map is likely to continue to exhibit an

efficiency gap in favor of that party for the rest of the decade. Jd.

48a-50a. And they presented evidence of how Act 43's efficiency

gap would change if citizens shifted their votes in accordance

with historical patterns of vote shifts in Wisconsin. Jd. 47a-48a.

claims, we believe a justiciable standard also requires

proof of lack of responsiveness and causation.

As with asymmetry, given the evidence available

to the district court, there is no need here to rely on

any kind of predictions to assess responsiveness. Re-

sponsiveness can be observed directly based on elec-

tion outcomes under the challenged map. In contrast,

in each of the Court’s prior partisan gerrymandering

cases, only one election or no election had occurred

under the challenged plan. See LULAC, 548 U.S. at

413 (opinion of Kennedy, J.) (one); Vieth, 541 U.S. at

272 (plurality) (none); Bandemer, 478 U.S. at 115

(plurality) (one). We continue to believe that experts

can reliably assess the responsiveness and asym-

metry of a newly enacted map by projecting the re-

sults of recent past statewide races onto the new

district lines, especially in light of current extraordi-

narily high levels of partisan polarization. See supra

note 5. But, when multiple elections under the chal-

lenged map have already occurred—in the instant

case, there have been three—tthere is no need for such

projections. Courts and expert witnesses can analyze

actual election results for any disparate and durable

effects on disfavored voters.

As to causation—or the absence of any neutral

justification—the only evidence of causation in LU-

LAC involved comparing the challenged plan to the

prior map. There was no evidence isolating the degree

of asymmetry that occurred from neutral redistricting

criteria or chance. LULAC, 548 U.S. at 451-52 (Ste-

vens, J., concurring in part and dissenting in part);

see also J.A., LULAC, 2006 WL 64437, at *36-39 (re-

port of Professor John R. Alford, expert for plaintiffs);

id, at *224-25 (testimony of Professor Gaddie, expert

for the State).

Now, not only are traditional tests of statistical

significance available for partisan asymmetry, vastly

improved computing power permits experts to create

thousands (or even many millions) of computer-gen-

crated alternative maps. These can then be screened

to consider only those plans that satisfy all standard

districting criteria to at least the same extent as the

challenged plan, establishing the neutral benchmark

against which to measure the magnitude of “man-

made” asymmetry in the treatment of different blocs

of voters. Using these alternative maps, we can say

with a high degree of statistical confidence whether a

given quantum of asymmetry is explainable by some-

thing other than invidious intent.

For example, some of the most advanced work in

the field is that of Jowei Chen and Jonathan Rodden.

They generate thousands of maps with simulated dis-

trict lines that can control for “all legal criteria and

requirements in redistricting’—maps that are at

least as good as the challenged plan on all neutral cri-

teria. Chen & Rodden, supra, at 335. By “measuring

the partisan[] [asymmetry] of these [computer-gener-

ated] plans and contrast[ing] them with that of the

plan in question,” one can determine, with a high de-

gree of statistical confidence, the extent to which the

challenged plan exhibits asymmetry over and above

the neutral baseline. Chen & Rodden, supra, at 338.

Moreover, “[a]ny natural geographic advantage for

one party or another will be expressed in the parti-

sanship of the simulated plans.” Jd. Other scholars,

such as Professor Wendy Tam Cho, have done very

similar computations, involving an even larger num-

ber of alternative maps. Wendy Tam Cho et al., A Rea-

sonable Bias Approach to Gerrymandering: Using

Automated Plan Generation to Evaluate Redistricting

Proposals, 59 William & Mary L. Rev. (forthcoming

2017) (generating millions of alternative maps); see

also Jonathan Mattingly et al., Quantifying Gerry-

mandering, https://tinyurl.com/yc4cvxkg (last visited

Aug. 10, 2017) (generating 150,000 to 200,000 alter-

native maps for various states).

This mechanism of isolating causation was not

feasible at the time of LULAC. Now, with dramatic

improvements in computer processing § speed,

memory, and storage, we can produce thousands of

maps in minutes. Notably, Professor Chen applied his

methodology to Wisconsin’s Act 43 and concluded that

the “levels of natural electoral bias pale in comparison

to the much more extreme electoral bias exhibited by

the Act 43 plan.” Jowei Chen, The Impact of Political

Geography on Wisconsin Redistricting: An Analysis of

Wisconsin’s Act 43 Assembly Districting Plan, Elec-

tion L.J. (forthcoming 2017) (manuscript at 3),

https://tinyurl.com/y7ohowmy.

kke

State-of-the-art analytical tools now capture all

the relevant information for detecting and precisely

measuring the disparate effect of partisan gerryman-

ders. In particular, the various methods of measuring

asymmetry are fundamentally complementary. Some

are more complex in their calculations than others.

But they all measure the same thing: the magnitude

of the disparate burden (if any) that a challenged map

imposes on a political party and its supporters. And

they all converge in conclusions in the face of an egre-

gious partisan gerrymander. In the rare circumstance

that one method is unsuitable to a particular context,

another can be used instead.

While the methodology will continue to improve,

future advances are likely to be incremental only—

the equivalent of adding a further decimal point to an

already precise figure—and will not materially alter

the calculus. Moreover, experts can clearly and con-

sistently apply existing statistical tools to assess

whether each element—-partisan asymmetry, lack of

responsiveness, and causation—is met. Once the

Court adopts a legal standard for justiciable partisan

gerrymandering claims, it will be relatively straight-

forward for competent experts to provide their assess-

ments of whether that standard is met in a given case.

CONCLUSION

For the foregoing reasons, the Court should hold

that partisan gerrymander claims are justiciable, and

it should adopt a standard that makes partisan asym-

metry, lack of responsiveness, and causation neces-

sary elements of such a claim.

Thomas M. Bondy

Avi Daniel Rosenblit

ORRICK, HERRINGTON &

SUTCLIFFE LLP

1152 15th Street

Washington, DC 20005

August 10, 2017

Respectfully submitted,

E. Joshua Rosenkranz

Counsel of Record

Rachel Wainer Apter

Hannah Garden-

Monheit