(Slip Opinion)              OCTOBER TERM, 2015                                       1

                                       Syllabus

         NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
       being done in connection with this case, at the time the opinion is issued.
       The syllabus constitutes no part of the opinion of the Court but has been
       prepared by the Reporter of Decisions for the convenience of the reader.
       See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.


SUPREME COURT OF THE UNITED STATES

                                       Syllabus

         HARRIS ET AL. v. ARIZONA INDEPENDENT 

           REDISTRICTING COMMISSION ET AL. 


 ON APPEAL FROM THE UNITED STATES DISTRICT COURT FOR
               THE DISTRICT OF ARIZONA

    No. 14–232.      Argued December 8, 2015—Decided April 20, 2016
After the 2010 census, Arizona’s independent redistricting commission
  (Commission), comprising two Republicans, two Democrats, and one
  Independent, redrew Arizona’s legislative districts, with guidance
  from legal counsel, mapping specialists, a statistician, and a Voting
  Rights Act specialist. The initial plan had a maximum population
  deviation from absolute equality of districts of 4.07%, but the Com-
  mission adopted a revised plan with an 8.8% deviation on a 3-to-2
  vote, with the Republican members dissenting. After the Depart-
  ment of Justice approved the revised plan as consistent with the Vot-
  ing Rights Act, appellants filed suit, claiming that the plan’s popula-
  tion variations were inconsistent with the Fourteenth Amendment.
  A three-judge Federal District Court entered judgment for the Com-
  mission, concluding that the “deviations were primarily a result of
  good-faith efforts to comply with the Voting Rights Act . . . even
  though partisanship played some role.”
Held: The District Court did not err in upholding Arizona’s redistricting
  plan. Pp. 3–11.
     (a) The Fourteenth Amendment’s Equal Protection Clause requires
  States to “make an honest and good faith effort to construct [legisla-
  tive] districts . . . as nearly of equal population as is practicable,”
  Reynolds v. Sims, 377 U. S. 533, 577, but mathematical perfection is
  not required. Deviations may be justified by “legitimate considera-
  tions,” id., at 579, including “traditional districting principles such as
  compactness [and] contiguity,” Shaw v. Reno, 509 U. S. 630, 647, as
  well as a state interest in maintaining the integrity of political subdi-
  visions, Mahan v. Howell, 410 U. S. 315, 328, a competitive balance
  among political parties, Gaffney v. Cummings, 412 U. S. 735, 752,
2                 HARRIS v. ARIZONA INDEPENDENT
                     REDISTRICTING COMM’N                                 

                               Syllabus


    and, before Shelby County v. Holder, 570 U. S. ___, compliance with
    §5 of the Voting Rights Act. It was proper for the Commission to pro-
    ceed on the last basis here. In addition, “minor deviations from
    mathematical equality”—i.e., deviations “under 10%,” Brown v.
    Thomson, 462 U. S. 835, 842—do not, by themselves, “make out a
    prima facie case of invidious discrimination under the Fourteenth
    Amendment [requiring] justification by the State,” Gaffney, supra, at
    745. Because the deviation here is under 10%, appellants cannot rely
    upon the numbers to show a constitutional violation. Instead, they
    must show that it is more probable than not that the deviation re-
    flects the predominance of illegitimate reapportionment factors ra-
    ther than “legitimate considerations.” Pp. 3–5.
       (b) Appellants have failed to meet that burden here, where the rec-
    ord supports the District Court’s conclusion that the deviations pre-
    dominantly reflected Commission efforts to achieve compliance with
    the Voting Rights Act, not to secure political advantage for the Dem-
    ocratic Party. To meet the Voting Rights Act’s nonretrogression re-
    quirement, a new plan, when compared to the current plan (bench-
    mark plan), must not diminish the number of districts in which
    minority groups can “elect their preferred candidates of choice” (abil-
    ity-to-elect districts). A State can obtain legal assurance that it has
    satisfied this requirement if it submits its proposed plan to the Jus-
    tice Department and the Department does not object to the plan. The
    record shows that the Commission redrew the initial map to ensure
    that the plan had 10 ability-to-elect districts, the same number as the
    benchmark plan. But after a statistician reported that the Justice
    Department still might not agree with the plan, the Commission
    changed additional boundaries, causing District 8, a Republican lean-
    ing district, to become more politically competitive. Because this rec-
    ord well supports the District Court’s finding that the Commission
    was trying to comply with the Voting Rights Act, appellants have not
    shown that it is more probable than not that illegitimate considera-
    tions were the predominant motivation for the deviations. They have
    thus failed to show that the plan violates the Equal Protection
    Clause. Pp. 5–9.
       (c) Appellants’ additional arguments are unpersuasive. While Ari-
    zona’s Democratic-leaning districts may be somewhat underpopulat-
    ed and its Republican-leaning districts somewhat overpopulated,
    these variations may reflect only the tendency of Arizona’s 2010 mi-
    nority populations to vote disproportionately for Democrats and thus
    can be explained by the Commission’s efforts to maintain at least 10
    ability-to-elect districts. Cox v. Larios, 542 U. S. 947, in which the
    Court affirmed a District Court’s conclusion that a Georgia reappor-
    tionment plan violated the Equal Protection Clause where its devia-
                     Cite as: 578 U. S. ____ (2016)                   3

                                  Syllabus

  tion, though less than 10%, resulted from the use of illegitimate fac-
  tors, is inapposite because appellants have not carried their burden
  of showing the use of illegitimate factors here. And because Shelby
  County was decided after Arizona’s plan was created, it has no bear-
  ing on the issue whether the State’s attempt to comply with the Vot-
  ing Rights Act is a legitimate state interest. Pp. 9–11.
993 F. Supp. 2d 1042, affirmed.

  BREYER, J., delivered the opinion for a unanimous Court.
                        Cite as: 578 U. S. ____ (2016)                              1

                             Opinion of the Court

     NOTICE: This opinion is subject to formal revision before publication in the
     preliminary print of the United States Reports. Readers are requested to
     notify the Reporter of Decisions, Supreme Court of the United States, Wash-
     ington, D. C. 20543, of any typographical or other formal errors, in order
     that corrections may be made before the preliminary print goes to press.


SUPREME COURT OF THE UNITED STATES
                                   _________________

                                   No. 14–232
                                   _________________


     WESLEY W. HARRIS, ET AL., APPELLANTS v. 

     ARIZONA INDEPENDENT REDISTRICTING 

              COMMISSION, ET AL. 

ON APPEAL FROM THE UNITED STATES DISTRICT COURT FOR
              THE DISTRICT OF ARIZONA
                                 [April 20, 2016]

   JUSTICE BREYER delivered the opinion of the Court.
   Appellants, a group of Arizona voters, challenge a re-
districting plan for the State’s legislature on the ground
that the plan’s districts are insufficiently equal in popula-
tion. See Reynolds v. Sims, 377 U. S. 533, 577 (1964).
Because the maximum population deviation between the
largest and the smallest district is less than 10%, the
appellants cannot simply rely upon the numbers to show
that the plan violates the Constitution. See Brown v.
Thomson, 462 U. S. 835, 842 (1983). Nor have appellants
adequately supported their contentions with other evi-
dence. We consequently affirm a 3-judge Federal District
Court decision upholding the plan.
                             I
  In 2000, Arizona voters, using the initiative process,
amended the Arizona Constitution to provide for an inde-
pendent redistricting commission. See Arizona State
Legislature v. Arizona Independent Redistricting Comm’n,
576 U. S. ___, ___ (2015) (slip op., at 35) (upholding the
amendment as consistent with federal constitutional and
2            HARRIS v. ARIZONA INDEPENDENT
                REDISTRICTING COMM’N                         

                    Opinion of the Court 


statutory law). Each decade, the Arizona Commission on
Appellate Court Appointments creates three slates of
individuals: one slate of 10 Republicans, one slate of 10
Democrats, and one slate of 5 individuals not affiliated
with any political party. The majority and minority leader
of the Arizona Legislature each select one Redistricting
Commission member from the first two lists. These four
selected individuals in turn choose one member from the
third, nonpartisan list. See Ariz. Const., Art. IV, pt. 2,
§§1(5)–(8). Thus, the membership of the Commission
consists of two Republicans, two Democrats, and one
independent.
   After each decennial census, the Commission redraws
Arizona’s 30 legislative districts. The first step in the
process is to create “districts of equal population in a grid-
like pattern across the state.” §1(14). It then adjusts the
grid to “the extent practicable” in order to take into ac-
count the need for population equality; to maintain geo-
graphic compactness and continuity; to show respect for
“communities of interest”; to follow locality boundaries;
and to use “visible geographic features” and “undivided . . .
tracts.” §§1(14)(B)–(E). The Commission will “favo[r]”
political “competitive[ness]” as long as its efforts to do so
“create no significant detriment to the other goals.” Id.,
§1(14)(F). Finally, it must adjust boundaries “as neces-
sary” to comply with the Federal Constitution and with
the federal Voting Rights Act. §1(14)(A).
   After the 2010 census, the legislative leadership selected
the Commission’s two Republican and two Democratic
members, who in turn selected an independent member,
Colleen Mathis. Mathis was then elected chairwoman.
The Commission hired two counsel, one of whom they
thought of as leaning Democrat and one as leaning Repub-
lican. It also hired consultants, including mapping spe-
cialists, a statistician, and a Voting Rights Act specialist.
With the help of its staff, it drew an initial plan, based
                  Cite as: 578 U. S. ____ (2016)              3

                      Opinion of the Court

upon the gridlike map, with district boundaries that pro-
duced a maximum population deviation (calculated as the
difference between the most populated and least populated
district) of 4.07%. After changing several boundaries,
including those of Districts 8, 24, and 26, the Commission
adopted a revised plan by a vote of 3 to 2, with the two
Republican members voting against it. In late April 2012,
the Department of Justice approved the plan as consistent
with the Voting Rights Act.
   The next day, appellants filed this lawsuit, primarily
claiming that the plan’s population variations were incon-
sistent with the Fourteenth Amendment. A 3-judge Fed-
eral District Court heard the case. See 28 U. S. C.
§2284(a) (providing for the convention of such a court
whenever an action is filed challenging the constitutional-
ity of apportionment of legislative districts). After a 5-day
bench trial, the court, by a vote of 2 to 1, entered judgment
for the Commission. The majority found that “the popula-
tion deviations were primarily a result of good-faith efforts
to comply with the Voting Rights Act . . . even though
partisanship played some role.” 993 F. Supp. 2d 1042,
1046 (Ariz. 2014). Appellants sought direct review in this
Court. See 28 U. S. C. §1253. We noted probable jurisdic-
tion on June 30, 2015, and we now affirm.
                               II

                               A

  The Fourteenth Amendment’s Equal Protection Clause
requires States to “make an honest and good faith effort to
construct [legislative] districts . . . as nearly of equal popu-
lation as is practicable.” Reynolds, 377 U. S., at 577. The
Constitution, however, does not demand mathematical
perfection. In determining what is “practicable,” we have
recognized that the Constitution permits deviation when it
is justified by “legitimate considerations incident to the
effectuation of a rational state policy.” Id., at 579. In
4            HARRIS v. ARIZONA INDEPENDENT
                REDISTRICTING COMM’N                         

                    Opinion of the Court 


related contexts, we have made clear that in addition to
the “traditional districting principles such as compactness
[and] contiguity,” Shaw v. Reno, 509 U. S. 630, 647 (1993),
those legitimate considerations can include a state inter-
est in maintaining the integrity of political subdivisions,
Mahan v. Howell, 410 U. S. 315, 328 (1973), or the compet-
itive balance among political parties, Gaffney v. Cum-
mings, 412 U. S. 735, 752 (1973). In cases decided before
Shelby County v. Holder, 570 U. S. ___ (2013), Members of
the Court expressed the view that compliance with §5 of
the Voting Rights Act is also a legitimate state considera-
tion that can justify some deviation from perfect equality
of population. See League of United Latin American Citi-
zens v. Perry, 548 U. S. 399, 518 (2006) (SCALIA, J., con-
curring in judgment in part and dissenting in part, joined
in relevant part by ROBERTS, C. J., THOMAS & ALITO, JJ.);
id., at 475, n. 12 (Stevens, J., concurring in part and dis-
senting in part, joined in relevant part by BREYER, J.); id.,
at 485 n. 2 (Souter, J., concurring in part and dissenting in
part, joined by GINSBURG, J.); see also Vieth v. Jubelirer,
541 U. S. 267, 284 (2004) (plurality opinion) (listing exam-
ples of traditional redistricting criteria, including “compli-
ance with requirements of the [Voting Rights Act]”). It was
proper for the Commission to proceed on that basis here.
   We have further made clear that “minor deviations from
mathematical equality” do not, by themselves, “make out a
prima facie case of invidious discrimination under the
Fourteenth Amendment so as to require justification by
the State.” Gaffney, supra, at 745. We have defined as
“minor deviations” those in “an apportionment plan with a
maximum population deviation under 10%.” Brown, 462
U. S., at 842. And we have refused to require States to
justify deviations of 9.9%, White v. Regester, 412 U. S. 755,
764 (1973), and 8%, Gaffney, 412 U. S., at 751. See also
Fund for Accurate and Informed Representation, Inc. v.
Weprin, 506 U. S. 1017 (1992) (summarily affirming a
                 Cite as: 578 U. S. ____ (2016)            5

                     Opinion of the Court

District Court’s finding that there was no prima facie case
where the maximum population deviation was 9.43%).
   In sum, in a case like this one, those attacking a state-
approved plan must show that it is more probable than not
that a deviation of less than 10% reflects the predomi-
nance of illegitimate reapportionment factors rather than
the “legitimate considerations” to which we have referred
in Reynolds and later cases. Given the inherent difficulty
of measuring and comparing factors that may legitimately
account for small deviations from strict mathematical
equality, we believe that attacks on deviations under 10%
will succeed only rarely, in unusual cases. And we are not
surprised that the appellants have failed to meet their
burden here.
                              B
   Appellants’ basic claim is that deviations in their appor-
tionment plan from absolute equality of population reflect
the Commission’s political efforts to help the Democratic
Party. We believe that appellants failed to prove this
claim because, as the district court concluded, the devia-
tions predominantly reflected Commission efforts to
achieve compliance with the federal Voting Rights Act, not
to secure political advantage for one party. Appellants
failed to show to the contrary. And the record bears out
this conclusion. Cf. Anderson v. Bessemer City, 470 U. S.
564, 573 (1985) (explaining that a district court’s factual
finding as to whether discrimination occurred will not be
set aside by an appellate court unless clearly erroneous).
   The Voting Rights Act, among other things, forbids the
use of new reapportionment plans that “would lead to a
retrogression in the position of racial minorities with
respect to their effective exercise of the electoral fran-
chise.” Reno v. Bossier Parish School Bd., 520. U. S. 471,
478 (1997). A plan leads to impermissible retrogression
when, compared to the plan currently in effect (typically
6            HARRIS v. ARIZONA INDEPENDENT
                REDISTRICTING COMM’N                         

                    Opinion of the Court 


called a “benchmark plan”), the new plan diminishes the
number of districts in which minority groups can “elect
their preferred candidates of choice” (often called “ability-
to-elect” districts). See 52 U. S. C. §10304(b). A State can
obtain legal assurance that it has satisfied the non-
retrogression requirement if it submits its proposed plan
to the Federal Department of Justice, and the Department
does not object to the plan within 60 days. See 28 C. F. R.
§§51.9, 51.52(b) (2015). While Shelby County struck down
the §4(b) coverage formula, that decision came after the
maps in this case were drawn.
   The record in this case shows that the gridlike map that
emerged after the first step of the redistricting process
had a maximum population deviation from absolute equal-
ity of districts of 4.07%. After consulting with their Voting
Rights Act expert, their mapping consultant, and their
statisticians, all five Commissioners agreed that they
must try to obtain Justice Department Voting Rights Act
“preclearance” and that the former benchmark plan con-
tained 10 ability-to-elect districts. They consequently set
a goal of 10 such districts for the new plan. They then
went through an iterative process, involving further con-
sultation, to adjust the plan’s initial boundaries in order to
enhance minority voting strength. In October 2011 (by a
vote of 4 to 1), they tentatively approved a draft plan with
adjusted boundaries. They believed it met their goal of 10
ability-to-elect districts. And they published the plan for
public comment.
   In the meantime, however, the Commission received a
report from one of its statisticians suggesting that the
Department of Justice might not agree that the new pro-
posed plan contained 10 ability-to-elect districts. It was
difficult to know for certain because the Justice Depart-
ment did not tell States how many ability-to-elect districts
it believed were present in a benchmark plan, and neither
did it typically explain precisely and specifically how it
                  Cite as: 578 U. S. ____ (2016)            7

                      Opinion of the Court

would calculate the number that exist in a newly submit-
ted plan. See 76 Fed. Reg. 7470–7471 (2011). At the same
time, the ability-to-elect analysis was complex, involving
more than simply adding up census figures. The Depart-
ment of Justice instead conducted a “functional analysis of
the electoral behavior within the particular . . . election
district,” id., at 7471, and so might, for example, count as
ability-to-elect districts “crossover” districts in which
white voters combine their votes with minorities, see
Bartlett v. Strickland, 556 U. S. 1, 13–14 (2009). Its calcu-
lations might take into account group voting patterns,
electoral participation, election history, and voter turnout.
See 76 Fed. Reg., 7471. The upshot was not random
decision-making but the process did create an inevitable
degree of uncertainty. And that uncertainty could lead a
redistricting commission, as it led Arizona’s, to make
serious efforts to make certain that the districts it believed
were ability-to-elect districts did in fact meet the criteria
that the Department might reasonably apply. Cf. Ala-
bama Legislative Black Caucus v. Alabama, 575 U. S. ___,
___ (2015) (slip op., at 22) (“The law cannot insist that a
state legislature, when redistricting, determine precisely
what percent minority population §5 demands [because]
the standards of §5 are complex . . . . [To do so would] lay
a trap for an unwary legislature, condemning its redis-
tricting plan as either . . . unconstitutional racial gerry-
mandering [or] . . . retrogressive under §5”).
   As a result of the statistician’s report, the Commission
became concerned about certain of its proposed bounda-
ries. One of the Commission’s counsel advised that it
would be “prudent to stay the course in terms of the ten
districts that are in the draft map and look to . . .
strengthen them if there is a way to strengthen them.” 993
F. Supp. 2d, at 1058 (internal quotation marks omitted).
Subsequently, the Commission adopted several changes to
the boundaries of Districts 24 and 26. It reduced the
8            HARRIS v. ARIZONA INDEPENDENT 

                REDISTRICTING COMM’N                         

                    Opinion of the Court 


populations of those districts, thereby increasing the
percentage of Hispanic voters in each. The Commission
approved these changes unanimously.
   Changes in the boundaries of District 8, however,
proved more controversial. District 8 leaned Republican.
A Democrat-appointed Commissioner asked the mapping
specialist to look into modifications that might make
District 8 politically more competitive. The specialist
returned with a draft that shifted the boundary line be-
tween District 8 and District 11 so as to keep several
communities with high minority populations together in
District 8. The two Republican-appointed Commissioners
objected that doing so would favor Democrats by “hy-
perpacking” Republicans into other districts; they added
that the Commission should either favor political competi-
tiveness throughout the State or not at all. Id., at 1059
(internal quotation marks omitted).
   The Democrat-appointed proponent of the change re-
plied that District 8 had historically provided minority
groups a good opportunity to elect their candidate of
choice—an opportunity that the changes would preserve.
The Voting Rights Act specialist then said that by slightly
increasing District 8’s minority population, the Commis-
sion might be able to claim an 11th ability-to-elect district;
and that fact would “unquestionably enhance the submis-
sion and enhance chances for preclearance.” Ibid. (inter-
nal quotation marks omitted). The Commission’s counsel
then added that having another possible ability-to-elect
district could be helpful because District 26 was not as
strong an ability-to-elect district as the others. See ibid.
   Only then, after the counsel and consultants argued for
District 8 changes for the sake of Voting Rights Act pre-
clearance, did Chairwoman Mathis support those changes.
On that basis, the Commission ultimately approved the
changes to District 8 by a vote of 3 to 2 (with the two
Republican-appointed commissioners dissenting).           The
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                     Opinion of the Court

total population deviation among districts in this final
map was 8.8%. While the Commission ultimately con-
cluded that District 8 was not a true ability-to-elect dis-
trict, the State’s submission to the Department of Justice
cited the changes to District 8 in support of the argument
for preclearance. On April 26, 2012, the Department of
Justice precleared the submitted plan.
   On the basis of the facts that we have summarized, the
District Court majority found that “the population devia-
tions were primarily a result of good-faith efforts to com-
ply with the Voting Rights Act . . . even though partisan-
ship played some role.” 993 F. Supp. 2d, at 1046. This
conclusion was well supported in the record. And as a
result, appellants have not shown that it is more probable
than not that illegitimate considerations were the predom-
inant motivation behind the plan’s deviations from math-
ematically equal district populations—deviations that
were under 10%. Consequently, they have failed to show
that the Commission’s plan violates the Equal Protection
Clause as interpreted in Reynolds and subsequent cases.
                             C
   The appellants make three additional arguments. First,
they support their claim that the plan reflects unreason-
able use of partisan considerations by pointing to the fact
that almost all the Democratic-leaning districts are some-
what underpopulated and almost all the Republican-
leaning districts are somewhat overpopulated. That is
likely true. See 993 F. Supp. 2d, at 1049 (providing a
chart with percentage deviation figures by district). But
that fact may well reflect the tendency of minority popula-
tions in Arizona in 2010 to vote disproportionately for
Democrats. If so, the variations are explained by the
Commission’s efforts to maintain at least 10 ability-to-
elect districts. The Commission may have relied on data
from its statisticians and Voting Rights Act expert to
10           HARRIS v. ARIZONA INDEPENDENT 

                REDISTRICTING COMM’N                       

                    Opinion of the Court 


create districts tailored to achieve preclearance in which
minority voters were a larger percentage of the district
population. That might have necessitated moving other
voters out of those districts, thereby leaving them slightly
underpopulated. The appellants point to nothing in the
record to suggest the contrary.
   Second, the appellants point to Cox v. Larios, 542 U. S.
947 (2004), in which we summarily affirmed a district
court’s judgment that Georgia’s reapportionment of repre-
sentatives to state legislative districts violated the Equal
Protection Clause, even though the total population devia-
tion was less than 10%. In Cox, however, unlike the pre-
sent case, the district court found that those attacking the
plan had shown that it was more probable than not that
the use of illegitimate factors significantly explained
deviations from numerical equality among districts. The
district court produced many examples showing that
population deviation as well as the shape of many districts
“did not result from any attempt to create districts that
were compact or contiguous, or to keep counties whole, or
to preserve the cores of prior districts.” Id., at 949. No
legitimate purposes could explain them. It is appellants’
inability to show that the present plan’s deviations and
boundary shapes result from the predominance of simi-
larly illegitimate factors that makes Cox inapposite here.
Even assuming, without deciding, that partisanship is an
illegitimate redistricting factor, appellants have not car-
ried their burden.
   Third, appellants point to Shelby County v. Holder, 570
U. S. ___ (2013), in which this Court held unconstitutional
sections of the Voting Rights Act that are relevant to this
case. Appellants contend that, as a result of that holding,
Arizona’s attempt to comply with the Act could not have
been a legitimate state interest. The Court decided Shelby
County, however, in 2013. Arizona created the plan at
issue here in 2010. At the time, Arizona was subject to
                 Cite as: 578 U. S. ____ (2016)         11

                     Opinion of the Court

the Voting Rights Act, and we have never suggested the
contrary.
                      *     *   *
  For these reasons the judgment of the District Court is
affirmed.
                                         It is so ordered.
