Redistricting and the Supreme Court: The Most Significant Cases


redistricting map push-pins


Time was, redistricting was left to the near complete discretion of state lawmakers. However, over the past five decades, the United States Supreme Court has developed an extensive and complex jurisprudence on redistricting. 

Much of the case law is devoted to the constitutional requirement of one person, one vote, but over the past 20 years, more and more of the case law has addressed the impermissible uses of race in redistricting. In addition to the constitutional cases dealing with redistricting, the court has  addressed the requirements of the Voting Rights Act, one of the most significant pieces of legislation passed during the last half of the 20th  century. In its current term, the court will address once again whether or not standards for partisan gerrymandering can be determined and applied.

This page provides an overview of the most significant Supreme Court decisions on redistricting from the last five decades. These cases are grouped into four categories: cases relating to population, a case relating to using a redistricting commission, cases relating to race and cases relating to partisanship.

For more information on how states draw their legislative and congressional districts, see NCSL’s main redistricting page. For detailed information about litigation, see NCSL’s Redistricting Case Summaries. For case summaries from the current decade, see NCSL’s Redistricting Case Summaries: 2010 – Present.

Cases Relating to Population

Baker v. Carr, 369 U.S. 186 (1962)

Significance: For the first time, the court held that the federal courts had jurisdiction to consider constitutional challenges to state legislative redistricting plans.

Summary: Since the earliest days of the republic, redrawing the boundaries of legislative and congressional districts after each decennial census has been primarily the responsibility of state legislatures. Following World War I, as the nation’s population began to shift from rural to urban areas, many legislatures lost their enthusiasm for the decennial task and failed to carry out their constitutional responsibility. For decades, the U.S. Supreme Court declined repeated invitations to enter the “political thicket” of redistricting, Colegrove v. Green, (1946), and refused to order the legislatures to carry out their duty.

In this case, the Tennessee General Assembly had failed to reapportion seats in the Senate and House of Representatives since 1901. Baker v. Carr369 U.S. 186, 191. By 1960, population shifts in Tennessee made a vote in a small rural county worth 19 votes in a large urban county. Id. at 245. The Court held that a federal district court had jurisdiction to hear a claim that this inequality of representation violated the Equal Protection Clause of the Fourteenth Amendment.

Wesberry v. Sanders, 376 U.S. 1 (1964)

Significance: The Court held that the constitutionality of congressional districts was a question that could be decided by the courts.

Summary: Voters in Georgia’s Congressional District 5, which had three times the population of Congressional District 9, alleged that this imbalance denied them the full benefit of their right to vote. A three-judge federal district court held that drawing congressional districts was a task assigned by the Constitution to state legislatures, subject to guidance by Congress, and not assigned to the courts. The district court held that the complaint presented a “political question” the court had jurisdiction to decide, but should not. 376 U.S. at 2-3. The Supreme Court reversed, holding that congressional districts must be drawn so that “as nearly as is practicable one man’s vote in a congressional election is worth as much as another’s.” Id. at 7-8.

Reynolds v. Sims, 377 U.S. 533 (1964)

Significance: Both houses of a bicameral state legislature must be apportioned substantially according to population. Legislative districts may deviate from strict population equality only as necessary to give representation to political subdivisions and provide for compact districts of contiguous territory. Legislative districts should be redrawn to reflect population shifts at least every 10 years. Once a constitutional violation has been shown, a court should take equitable action to correct it, bearing in mind the practical requirements of running an election.

Summary: Alabama Senate and House seats had not been reapportioned among the counties since 1903. 377 U.S. at 539-40. Each county had one or more senators and one or more representatives, regardless of population. According to the 1960 Census, the largest Senate district had about 41 times the population of the smallest Senate district, and the largest House district had about 16 times the population of the smallest House district. Id. at 545.

Alabama attempted to justify the disparity in the Senate by analogy to the federal system, but the Supreme Court found that comparison to not be pertinent. Id. at 571-75. Justice Earl Warren declared, “Legislators represent people, not trees or acres.” Id. at 562.

The Court held that “the Equal Protection Clause requires that the seats in both houses of a bicameral state legislature must be apportioned on a population basis.” Id. at 568. More flexibility is allowed for legislative districts than for congressional districts. “[M]mathematical nicety is not a constitutional requisite” when drawing legislative plans. Id. at 569. All that is necessary is that the maps achieve “substantial equality of population among the various districts.” Id. at 579. Deviations from population equality in legislative plans may be justified if they are “based on legitimate considerations incident to the effectuation of a rational state policy,” such as maintaining the integrity of political subdivisions and providing for compact districts of contiguous territory. Id. at 578.

Redrawing legislative districts at least every 10 years to reflect population shifts is not constitutionally required, but to redraw them less often “would assuredly be constitutionally suspect.” Id. at 583-84.

Once a constitutional violation has been shown, a court should take equitable action to correct it, bearing in mind the practical requirements of running an election. Id. at 585.

Gaffney v. Cummings, 412 U.S. 735 (1973)

Significance: The court upheld a legislative redistricting plan in which the total deviation was 1.81 percent for the Senate and 7.83 percent for the House. This indicates that legislative plans with a total deviation of 10% or less are presumptively constitutional although 10 percent is not a safe harbor.

Summary: Connecticut voters challenged the 1971 redrawing of Senate and House districts by the Apportionment Board. The Senate districts had a total population deviation of 1.81 percent. The House districts had a total deviation of 7.83 percent. 412 U.S. at 737. The complaint alleged that the population deviations were larger than required by the Equal Protection Clause of the Fourteenth Amendment and split too many town boundaries. Id. at 738-39. The Supreme Court held that the Board was not required to justify population deviations of this magnitude. Id. at 740-51. In dissent, Justice William J. Brennan surveyed the various legislative plans whose total deviations the Court had approved or rejected and alleged it had established a ten-percent threshold: “deviations in excess of that amount are apparently acceptable only on a showing of justification by the State; deviations less than that amount require no justification whatsoever.” Id. at 777.

In later cases, the Court majority has endorsed and followed the rule Brennan’s dissent accused them of establishing. See, e.g.Chapman v. Meier420 U.S. 1 (1975); Connor v. Finch431 U.S. 407 (1977); Brown v. Thomson462 U.S. 835, -43 (1983); Voinovich v. Quilter507 U.S. 146 (1993).   Based on this line of cases, plans with a total deviation of 10% or less are presumptively constitutional.  But a total deviation of less than 10 percent is not a safe harbor; plaintiffs may rebut the presumption by providing other evidence of discrimination within the 10 percent. See Larios v. Cox, 300 F. Supp.2d 1320 (N.D. Ga. 2004), aff’d542 U.S. 947, 2004 (mem.). 

Karcher v. Daggett, 462 U.S. 725 (1983)

Significance: Congressional districts must be mathematically equal in population, unless necessary to achieve a legitimate state objective.

Summary: The New Jersey Legislature drew a congressional plan that had a total deviation of 3,674 people, or 0.6984 percent. 462 U.S. at 728. The Supreme Court held that parties challenging a congressional plan bear the burden of proving that population differences among districts could have been reduced or eliminated by a good-faith effort to draw districts of equal population. If the plaintiffs carry their burden, the state must then bear the burden of proving that each significant variance between districts was necessary to achieve some legitimate state objective. Brennan, now writing for the 5-4 majority, noted that complying with what we now call “traditional redistricting principles,” such as compactness, respecting municipal boundaries, preserving the cores of prior districts and avoiding contests between incumbents, could meet the state’s burden. 462 U.S. 740-41.

Evenwel v. Abbott, 136 S. Ct. 1120 (2016)

Significance: Total population is a permissible metric for calculating compliance with “one person, one vote.” 

Summary: Since Reynolds and Wesberry, states have almost universally used total population as the unit for calculating population equality for districting plans. Plaintiffs in Evenwel challenged Texas’s 2011 redistricting scheme, arguing that its use of total population violated the Equal Protection Clause by discriminating against voters in districts with low immigrant populations by giving voters in districts with significant immigrant populations a disproportionately weighted vote. The Supreme Court held that its past opinions confirmed that states may use total population in order to comply with one person, one vote. The court did not hold that other methods are impermissible. 

Cases Relating to Legislatures vs. Commissions

Arizona State Legislature v. Arizona Independent Redistricting Commission, No. 13-1314, 576 U.S. , 135 S. Ct. 2652 (2015)

Significance: The creation of a redistricting commission for congressional districts via ballot initiative does not violate the Elections Clause of the U.S. Constitution.

Summary: In 2000, Arizona voters created the Arizona Independent Redistricting Commission via ballot initiative to redraw state legislative districts and congressional districts. In 2015, the Arizona Legislature challenged the right of the commission to draft congressional lines, arguing that the Elections Clause of the U.S. Constitution only grants two institutions the power to regulate the time, place, or manner of electing congressional representatives: the legislatures in each of the states, or Congress. The Supreme Court held that the reference to the “Legislature” in the Elections Clause encompassed citizen initiatives in states like Arizona, where the state constitution explicitly includes the people’s right to bypass the legislature and make laws directly through such initiatives. 

Cases Relating to Race 

Thornburg v. Gingles, 478 U.S. 30 (1986)

Significance: This case created the standard for determining whether § 2 of the Voting Rights Act requires that a majority-minority district be drawn.

Summary: Following the 1982 amendments to the Voting Rights Act (VRA), it was unclear precisely when the VRA would require a majority-minority district be drawn to prevent vote dilution. Here, the Supreme Court held that for a plaintiff to prevail on a § 2 claim, he or she must show:

  1. The racial or language minority group “is sufficiently numerous and compact to form a majority in a single-member district.”
  2. The minority group is “politically cohesive,” meaning its members tend to vote similarly.
  3. The “majority votes sufficiently as a bloc to enable it…usually to defeat the minority’s preferred candidate.”


A later case, Bartlett v. Strickland, 556 U.S. 1 (2009), added the requirement that a minority group be a numerical majority of the voting-age population in order for § 2 of the Voting Rights Act to apply.

Shaw v. Reno, 509 U.S. 630 (1993) 

Significance: Legislative and congressional districts will be struck down by courts for violating the Equal Protection Clause if they cannot be explained on grounds other than race. While not dispositive, “bizarrely shaped” districts are strongly indicative of racial intent.

Summary: Plaintiffs brought a novel legal claim, arguing that a North Carolina congressional district was so bizarrely shaped that it amounted to a “racial gerrymander,” which they claimed violated the Equal Protection Clause. The Court rejected the state’s defense that the district was justified as a so-called “majority-minority district,” holding that the Voting Rights Act required no such district to be drawn where one did not previously exist. Claiming the North Carolina district resembled “the most egregious racial gerrymanders of the past,” the court struck down the district on the basis that it reflected the incorrect belief that members of minority groups in different geographic areas (e.g. Durham vs. Charlotte) had the same interests, and did not have independent local needs that would be better served by having a more locally-oriented representative.

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

Significance: A district becomes an unconstitutional racial gerrymander if race was the “predominant” factor in the drawing of its lines.

Summary: Following Shaw, it remained unclear what the standard of review was under the new racial gerrymandering doctrine. In Miller, the U.S. Department of Justice in 1991 refused preclearance to Georgia’s initial congressional redistricting plan under § 5 of the Voting Rights Act, claiming the state needed to create an additional majority-minority district. Plaintiffs challenged the newly drawn districts as racial gerrymanders. The Supreme Court held for the plaintiffs, and established the rule for racial gerrymandering claims: if a district is drawn predominantly on the basis of race, it violates the Equal Protection Clause.

Bush v. Vera, 517 U.S. 952 (1996)

Significance: If you want to argue that partisan politics, not race, was your dominant motive in drawing district lines, beware of using race as a proxy for political affiliation. To survive strict scrutiny under the Equal Protection Clause and avoid being struck down as a racial gerrymander, a district must be reasonably compact.

Summary: Under the 1990 reapportionment of seats in Congress, Texas was entitled to three additional congressional districts. The Texas Legislature decided to draw one new Hispanic-majority district in South Texas, one new African-American-majority district in Dallas County, and one new Hispanic-majority district in the Houston area. In addition, the legislature reconfigured a district in the Houston area to increase its percentage of African Americans. The legislature used sophisticated software that allowed it to redistrict with racial data at the census block level. Plaintiffs challenged 24 of the state’s 30 congressional districts as racial gerrymanders. The Supreme Court struck down three districts, holding that race was the predominant factor in drawing the lines. In these districts, the court concluded that districts drawn to satisfy Section 2 of the VRA must not subordinate traditional redistricting principles more than reasonably necessary. The districts in question were in the courts words, “bizarrely shaped and far from compact.” These characteristics were predominately attributable to racially motivated gerrymandering.

Shelby County v. Holder, No. 12-96570 U.S. 529 (2013)

Significance: Section 5 of the Voting Rights Act no longer applies to any jurisdictions in the United States. As a result, redistricting plans and other changes in voting laws, such as voter identification requirements, need not be approved before they take effect.

Summary: Section 5 of the Voting Rights Act of 1965 (VRA) (codified as amended at 52 U.S.C. § 10304), prohibits certain states and political subdivisions from changing any voting law or practice without first obtaining from either the U.S. Attorney General or the U.S. District Court for the District of Columbia a determination that the change neither had the purpose nor would have the effect of denying or abridging the right to vote on account of race or color, or membership in a language minority group. (A “language minority group” is defined as “American Indian, Asian American, Alaskan Natives or of Spanish heritage.” 52 U.S.C. § 10310(c)(3) (2018)). This process is called “preclearance.” A redistricting plan had to be precleared before it could take effect. Section 5 applies only to certain jurisdictions in the South and elsewhere that meet the requirements of § 4(b) (codified as amended at 52 U.S. C. § 10303(b)): the jurisdiction had imposed a literacy test or similar requirement making it difficult to vote and less than 50 percent of its voting-age population had been registered to vote or had voted in the presidential election of 1964, 1968, or 1972 (depending on when the jurisdiction first became subject to § 5).

In 2011, Shelby County, Alabama, challenged the constitutionality of both the formula that determined whether § 5 applied to a jurisdiction—§ 4(b)—and § 5 itself. It alleged that the coverage formula in § 4(b) had not changed since the VRA was enacted in 1965, that conditions in Shelby County had changed drastically since then, and that standards based on old data should no longer apply.

The Supreme Court held that § 4(b) was unconstitutional. It balanced the exceptional conditions surrounding implementation of the Voting Rights Act with the basic principles of the 10th Amendment. The 10th Amendment reserves to the states all powers not specifically granted to the federal government. This includes the power to regulate elections. In addition, the principle of equal sovereignty among the states frowns upon their disparate treatment. It also found that the exceptional conditions that gave rise to the Voting Rights Act no longer existed.

Post-Shelby, it is still possible that states or jurisdictions could be “bailed in” under § 3 of the VRA for preclearance, if a pattern of current discrimination is found.

Alabama Legislative Black Caucus v. Alabama, No. 13-895, 575 U.S. ___, 135 S. Ct. 1257 (2015)

Significance: Racial gerrymandering claims proceed district-by-district, not against an entire plan. Further, equal population is not a “factor to be considered” when redistricting, but rather a constitutional mandate. Section 5 of the Voting Rights Act does not require a covered jurisdiction to maintain a specific numerical minority percentage when redistricting.

SummaryThe district court upheld an Alabama Legislative redistricting plan that tried to make populations nearly equal in the districts, and attempted to maintain the same black population percentages in these districts as those in the plan from the previous decade. The Supreme Court reversed and remanded the case to the district court for several reasons.

These reasons are:

  1. The district court’s analysis of the racial gerrymandering claim erroneously referred to the state “as a whole,” rather than district-by-district. Case law since Shaw v. Reno (see above) has made clear that racial gerrymandering claims are judged on a district-by-district basis.
  2. The state could not use its equal-population goal as a factor to be weighed against other factors when redistricting. Rather, equal population is a constitutional mandate that undergirds the entire redistricting process and can neither give way to other mandatory factors nor justify deviating from them.
  3. Respecting the state’s compelling interest to consider race in drawing districts so as to comply with Section 5 of the Voting Rights Act, the District Court, while understanding that a plan had to be narrowly tailored to meet the compelling interest test, asked the wrong question when it concluded that it must answer, “How can we maintain present minority percentages in majority-minority districts?”  The proper inquiry would have focused on the extent to which present percentages of minority voters had to be maintained to preserve a minority’s ability to elect a candidate of its choice?   Asking the wrong question, yielded the wrong answer. 


Cooper v. Harris, No. 15-1262, 581 U.S. ___, 137 S. Ct. 1455 (2017)

Significance: Partisanship cannot be used to justify a racial gerrymander. Further, § 2 of the Voting Rights Act requires that a racial minority have the opportunity to elect a “candidate of choice,” not that a particular percentage of minority voters be present in a district.  This case represents a synthesis of earlier cases on the requirements of Section 2 as set out in Gingles, and the now well-developed case law on racial gerrymandering that began with Shaw v. Reno.

Summary: Voters in two North Carolina congressional districts challenged their districts as unconstitutional racial gerrymanders. The state argued the case on two primary grounds. First, the state argued the increase in the percentage of black voters in the district was required to avoid a potential vote dilution challenge under Section 2 of the Voting Rights Act. Second, the state argued that any gerrymandering that had transpired was strictly partisan. The court rejected these arguments, holding that: (1) § 2 of the Voting Rights Act does not require a numerical majority of voters in a particular district; rather, it only requires that a compact and politically cohesive minority have the opportunity to elect its candidate of choice; and (2) Even if the underlying intent of the legislature in drawing maps is for partisan advantage and not with racial intent, the predominant use of race as a proxy for partisanship nonetheless constitutes racial gerrymandering.

Cases Related to Partisanship

Gaffney v. Cummings, 412 U.S. 735 (1973)

Significance: An otherwise acceptable reapportionment plan is not constitutionally vulnerable when its purpose is to provide districts that would achieve “political fairness” between the political parties.

Summary: Connecticut voters challenged the 1971 redrawing of Senate and House districts by the Apportionment Board. The board followed a policy of “political fairness,” using results from the preceding three statewide elections to create a number of Republican and Democratic legislative seats that would reflect as closely as possible the actual statewide plurality of votes for House and Senate candidates in a given election. 738. The complaint alleged that the plan was a political gerrymander that favored the Republican Party. Id. at 738-39. The Supreme Court held that a state’s attempt, within tolerable population limits, to fairly allocate political power to the parties in accordance with their voting strength is constitutional. Id. at 752-54.

It should be noted, that in Larios v. Cox, 300 F. Supp.2d 1320 (N.D. Ga. Feb. 10, 2004), aff’d 542 U.S. 947 (June 30, 2004), the United States Supreme Court affirmed without opinion a three-judge court decision holding unconstitutional a legislative plan within tolerable statistical limits (overall range less than 10%) when the legislature had departed from traditional redistricting principles and had discriminated against Republican incumbents.  In Larios, Plaintiffs challenged the 2001 congressional and House plans and the 2001 and 2002 Senate plans enacted by the Georgia General Assembly on various grounds. A three-judge federal district court upheld the congressional plan but struck down the legislative plans as a violation of the Equal Protection Clause of the Fourteenth Amendment to the U.S. Constitution. The order regarding the 2001 Senate plan was stayed pending preclearance of the plan. The overall range of both the 2001 House plan and the 2002 Senate plan was 9.98 percent, but the court found that the General Assembly had systematically underpopulated districts in rural South Georgia and inner-city Atlanta and overpopulated districts in the suburban areas north, east, and west of Atlanta in order to favor Democratic candidates and disfavor Republican candidates. The plans also systematically paired Republican incumbents while reducing the number of Democratic incumbents who were paired. The plans tended to ignore the traditional districting principles used in Georgia in previous decades, such as keeping districts compact, not allowing the use of point contiguity, keeping counties whole, and preserving the cores of prior districts.

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

Significance: Partisan gerrymandering claims may be brought in federal courts under the Equal Protection Clause. While a standard for measuring partisan gerrymanders was established, it was so difficult to satisfy that no partisan gerrymander was struck down under the Bandemer discriminatory effects test, which was abandoned in Vieth v. Jubelirer541 U.S. 267 (2004) (below). 

Summary: Democrats in Indiana challenged the 1981 legislative redistricting plan, claiming the district lines intentionally discriminated against them in violation of the Equal Protection Clause. The Supreme Court held that the claim was not a “political question,” and instead posed questions of law. The fact that a bright-line rule such as “one person, one vote” does not exist for partisanship did not mean that such challenges were non-justiciable political questions. The court required that, in order to prove partisan discrimination, a plaintiff political group must prove that those drawing a plan had an intent to discriminate against them, and that the plan had a discriminatory effect on them.

The court assumed that a discriminatory intent would not be hard to prove. As Justice Byron White said for the majority, "We think it most likely that whenever a legislature redistricts, those responsible for the legislation will know the likely political composition of the new districts and will have a prediction as to whether a particular district is a safe one for a Democratic or Republican candidate or is a competitive district that either candidate might win.” 478 U.S. at 128. On the other hand, a discriminatory effect, until at least publication, has been impossible to prove. The court said:

[U]constitutional discrimination occurs only when the electoral system is arranged in a manner that will consistently degrade a voter’s or a group of voters’ influences on the political process as a whole.

. . . Such a finding of unconstitutionality must be supported by evidence of continued frustration of the will of a majority of the voters or effective denial to a minority of voters of a fair chance to influence the political process. 478 U.S. at 132-33.

Merely showing that the minority is likely to lose elections held under the plan is not enough. As the Court pointed out, “the power to influence the political process is not limited to winning elections. . . . We cannot presume . . . without actual proof to the contrary, that the candidate elected will entirely ignore the interests of those voters [who did not vote for him or her].”

Vieth v. Jubelirer, 541 U.S. 267 (2004)

Significance: While a plurality of justices in this case held that partisan gerrymandering claims were non-justiciable, Justice Anthony Kennedy left the door open for potential future claims under the First Amendment, rather than the Fourteenth Amendment as had been cited in Bandemer.

Summary: Between Bandemer and Vieth, nearly 20 years elapsed. During that time, no lower court successfully created a manageable legal standard under which to scrutinize partisan gerrymanders. The majority of justices in this case held that this particular challenge also failed to prove a violation of the Constitution. Four of the five justices in the majority went further, stating that they believed no such standard existed and that partisan gerrymandering claims should be excluded from federal courts under the political question doctrine. However, the fifth justice in the majority—Kennedy—would not go that far. In his view, partisan gerrymandering claims might be justiciable, possibly under the First Amendment.   Nonetheless, he concluded that, “the failings of the many proposed standards for measuring the burden a gerrymander imposes on representational rights make our intervention improper. If workable standards do emerge to measure these burdens, however, courts should be prepared to order relief.”

Because Kennedy did not join the other four justices in the majority on this point, aggrieved parties continue to offer arguments for judicially manageable standards by which alleged political gerrymanders may be reviewed.

Rucho v. Common Cause, 139 S.Ct. 2484 (2019)

Significance: While state courts, Congress and state legislatures remain free to regulate partisanship in redistricting, claims of excessive partisanship are beyond the capacity of federal courts to resolve.

Summary: Ending the line of partisan gerrymandering cases that began with Davis v. Bandemer, a majority of justices held that because of the difficulty in ascertaining how much partisanship was too much, the question was too difficult for federal courts to answer—rendering such claims “non-justiciable” in federal courts. The majority opinion noted that this ruling applied only to federal courts, and that Congress, state legislatures and state courts may be better equipped to handle such questions. This ability to regulate partisanship in redistricting extends to ballot measures that circumvent the traditional legislative process.

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