About Redistricting


District lines are redrawn every 10 years following completion of the United States census. The federal government stipulates that districts must have nearly equal populations and must not discriminate on the basis of race or ethnicity.

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From Ballotpedia


  • As of November 2017, congressional redistricting was the province of the state legislatures in 37 states. In four states, independent commissions were responsible for congressional redistricting. In two states, the task fell to politician commissions. The remaining seven states contained one congressional district each, rendering congressional redistricting unnecessary.
  • As of November 2017, the legislatures themselves were responsible for state legislative redistricting in 37 states. In six states, the task fell to independent commissions. In seven states, politician commissions drew state legislative district maps.

See the sections below for further information on the following topics:

  1. Background: This section summarizes federal requirements for redistricting at both the congressional and state legislative levels. In addition, recent court decisions affecting redistricting policy are summarized.
  2. Methods: This section provides details about the various redistricting processes used in the states.
  3. Competitiveness: This section summarizes some of the arguments about the impact of redistricting on electoral competitiveness. Margin-of-victory and competitiveness data for congressional and state legislative elections is provided for informational purposes.
  4. Majority-minority districts: This section summarizes the legal basis for the creation of majority-minority districts and details some of the arguments surrounding the practice.


What is redistricting and what does it entail?

Federal requirements for congressional redistricting

According to Article I, Section 4 of the United States Constitution, the states and their legislatures have primary authority in determining the “times, places, and manner” of congressional elections. Congress may also pass laws regulating congressional elections.[2][3]

The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Places of chusing Senators.[4]
—United States Constitution

Article I, Section 2 of the United States Constitution stipulates that congressional representatives be apportioned to the states on the basis of population. There are 435 seats in the United States House of Representatives. Each state is allotted a portion of these seats based on the size of its population relative to the other states. Consequently, a state may gain seats in the House if its population grows or lose seats if its population decreases, relative to populations in other states. In 1964, the United States Supreme Court ruled in Wesberry v. Sanders that the populations of House districts must be equal “as nearly as practicable.”[5][6][7]

The equal population requirement for congressional districts is strict. According to All About Redistricting, “Any district with more or fewer people than the average (also known as the ‘ideal’ population), must be specifically justified by a consistent state policy. And even consistent policies that cause a 1 percent spread from largest to smallest district will likely be unconstitutional.”[7]

Federal requirements for state legislative redistricting

The United States Constitution is silent on the issue of state legislative redistricting. In the mid-1960s, the United States Supreme Court issued a series of rulings in an effort to clarify standards for state legislative redistricting. In Reynolds v. Sims, the court ruled that “the Equal Protection Clause [of the United States Constitution] demands no less than substantially equal state legislative representation for all citizens, of all places as well as of all races.” According to All About Redistricting, “it has become accepted that a [redistricting] plan will be constitutionally suspect if the largest and smallest districts [within a state or jurisdiction] are more than 10 percent apart.”[7]

State-based requirements

In addition to the federal criteria noted above, individual states may impose additional requirements on redistricting. Common state-level redistricting criteria are listed below.

  1. Contiguity refers to the principle that all areas within a district should be physically adjacent. A total of 49 states require that districts of at least one state legislative chamber be contiguous (Nevada has no such requirement, imposing no requirements on redistricting beyond those enforced at the federal level). A total of 23 states require that congressional districts meet contiguity requirements.[7][8]
  2. Compactness refers to the general principle that the constituents within a district should live as near to one another as practicable. A total of 37 states impose compactness requirements on state legislative districts; 18 states impose similar requirements for congressional districts.[7][8]
  3. community of interest is defined by FairVote as a “group of people in a geographical area, such as a specific region or neighborhood, who have common political, social or economic interests.” A total of 24 states require that the maintenance of communities of interest be considered in the drawing of state legislative districts. A total of 13 states impose similar requirements for congressional districts.[7][8]
  4. A total of 42 states require that state legislative district lines be drawn to account for political boundaries (e.g., the limits of counties, cities, and towns). A total of 19 states require that similar considerations be made in the drawing of congressional districts.[7][8]


In general, states vest one of the following three entities with redistricting authority:[9]

  1. State legislatures: In 37 of the 43 states required to conduct congressional redistricting, state legislatures have the final authority to draft and implement congressional district maps.[10] Likewise, in 37 of the 50 states, state legislatures are primarily responsible for state legislative redistricting. In these states, legislatures typically adopt district lines by a simple majority vote in each chamber. A state’s governor may usually veto the legislature’s redistricting plan.[11]
  2. Independent commissions: The composition of independent redistricting commissions varies from state to state. However, in all cases, the direct participation of elected officials is limited. Independent redistricting commissions exist in six states (in four of these states, independent commissions draw congressional and state legislative boundaries; in two, independent commissions draw only state legislative district boundaries).
  3. Politician commissions: The composition of politician redistricting commissions varies from state to state. For example, in some states, specific officials (e.g., governors, secretaries of state, etc.) are de facto commission members; in others, legislative leaders appoint other legislators to serve as commissioners. In all cases, elected officials may participate directly by sitting on the commissions. In two of the 43 states required to conduct congressional redistricting, politician commissions are responsible for drawing the maps. In seven states, politician commissions are responsible for state legislative redistricting.

Advisory commissions and backup commissions may also be involved in the redistricting process.


In 1812, Massachusetts Governor Elbridge Gerry signed into law a state senate district map that, according to the Encyclopædia Britannica, “consolidated the Federalist Party vote in a few districts and thus gave disproportionate representation to Democratic-Republicans.” The word gerrymander was coined by The Boston Gazette to describe the district.

See also: Gerrymandering

The term gerrymandering refers to the practice of drawing electoral district lines to favor one political party, individual, or constituency over another. When used in a rhetorical manner by opponents of a particular district map, the term has a negative connotation but does not necessarily address the legality of a challenged map. The term can also be used in legal documents; in this context, the term describes redistricting practices that violate federal or state laws.[1][12]

The phrase racial gerrymandering refers to the practice of drawing electoral district lines to dilute the voting power of racial minority groups. Federal law prohibits racial gerrymandering and establishes that, to combat this practice and to ensure compliance with the Voting Rights Act, states and jurisdictions can create majority-minority electoral districts. A majority-minority district is one in which a racial group or groups comprise a majority of the district’s populations. Racial gerrymandering and majority-minority districts are discussed in greater detail in this article.[13]

The phrase partisan gerrymandering refers to the practice of drawing electoral district maps with the intention of favoring one political party over another. In contrast with racial gerrymandering, on which the Supreme Court of the United States has issued rulings in the past affirming that such practices violate federal law, the high court had not, as of November 2017, issued a ruling establishing clear precedent on the question of partisan gerrymandering. Although the court has granted in past cases that partisan gerrymandering can violate the United States Constitution, it has never adopted a standard for identifying or measuring partisan gerrymanders. Partisan gerrymandering is described in greater detail in this article.[14][15]

Recent court decisions

See also: Redistricting cases heard by the Supreme Court of the United States

The following are summaries of recent court decisions dealing with redistricting policy, including questions relating to the consideration of race in drawing district maps, the use of total population tallies in apportionment, and the constitutionality of independent redistricting commissions. The rulings in these cases, which originated in a variety of states, impact redistricting processes across the nation.

Cooper v. Harris (2017)

See also: Cooper v. Harris

In Cooper v. Harris, decided on May 22, 2017, the Supreme Court of the United States affirmed the judgment of the United States District Court for the Middle District of North Carolina, finding that two of North Carolina’s congressional districts, the boundaries of which had been set following the 2010 United States Census, had been subject to an illegal racial gerrymander in violation of Section 2 of the Voting Rights Act. Justice Elena Kagan delivered the court’s majority opinion, which was joined by Justices Clarence ThomasRuth Bader GinsburgStephen Breyer, and Sonia Sotomayor (Thomas also filed a separate concurring opinion). In the court’s majority opinion, Kagan described the two-part analysis utilized by the high court when plaintiffs allege racial gerrymandering as follows: “First, the plaintiff must prove that ‘race was the predominant factor motivating the legislature’s decision to place a significant number of voters within or without a particular district.’ … Second, if racial considerations predominated over others, the design of the district must withstand strict scrutiny. The burden shifts to the State to prove that its race-based sorting of voters serves a ‘compelling interest’ and is ‘narrowly tailored’ to that end.” In regard to the first part of the aforementioned analysis, Kagan went on to note that “a plaintiff succeeds at this stage even if the evidence reveals that a legislature elevated race to the predominant criterion in order to advance other goals, including political ones.” Justice Samuel Alito delivered an opinion that concurred in part and dissented in part with the majority opinion. This opinion was joined by Chief Justice John Roberts and Justice Anthony Kennedy.[16][17][18]

Evenwel v. Abbott (2016)

See also: Evenwel v. Abbott

Evenwel v. Abbott was a case decided by the Supreme Court of the United States in 2016. At issue was the constitutionality of state legislative districts in Texas. The plaintiffs, Sue Evenwel and Edward Pfenninger, argued that district populations ought to take into account only the number of registered or eligible voters residing within those districts as opposed to total population counts, which are generally used for redistricting purposes. Total population tallies include non-voting residents, such as immigrants residing in the country without legal permission, prisoners, and children. The plaintiffs alleged that this tabulation method dilutes the voting power of citizens residing in districts that are home to smaller concentrations of non-voting residents. The court ruled 8-0 on April 4, 2016, that a state or locality can use total population counts for redistricting purposes. The majority opinion was penned by Justice Ruth Bader Ginsburg.[19][20][21][22]

Harris v. Arizona Independent Redistricting Commission (2016)

Justice Stephen Breyerpenned the majority opinion in Harris v. Arizona Independent Redistricting Commission.

See also: Harris v. Arizona Independent Redistricting Commission

Harris v. Arizona Independent Redistricting Commission was a case decided by the Supreme Court of the United States in 2016. At issue was the constitutionality of state legislative districts that were created by the commission in 2012. The plaintiffs, a group of Republican voters, alleged that “the commission diluted or inflated the votes of almost two million Arizona citizens when the commission intentionally and systematically overpopulated 16 Republican districts while under-populating 11 Democrat districts.” This, the plaintiffs argued, constituted a partisan gerrymander. The plaintiffs claimed that the commission placed a disproportionately large number of non-minority voters in districts dominated by Republicans; meanwhile, the commission allegedly placed many minority voters in smaller districts that tended to vote Democratic. As a result, the plaintiffs argued, more voters overall were placed in districts favoring Republicans than in those favoring Democrats, thereby diluting the votes of citizens in the Republican-dominated districts. The defendants countered that the population deviations resulted from legally defensible efforts to comply with the Voting Rights Act and obtain approval from the United States Department of Justice. At the time of redistricting, certain states were required to obtain preclearance from the U.S. Department of Justice before adopting redistricting plans or making other changes to their election laws—a requirement struck down by the United States Supreme Court in Shelby County v. Holder (2013). On April 20, 2016, the court ruled unanimously that the plaintiffs had failed to prove that a partisan gerrymander had taken place. Instead, the court found that the commission had acted in good faith to comply with the Voting Rights Act. The court’s majority opinion was penned by Justice Stephen Breyer.[23][24][25]

Arizona State Legislature v. Arizona Independent Redistricting Commission (2015)

See also: Arizona State Legislature v. Arizona Independent Redistricting Commission

Arizona State Legislature v. Arizona Independent Redistricting Commission was a case decided by the Supreme Court of the United States in 2015. At issue was the constitutionality of the Arizona Independent Redistricting Commission, which was established by state constitutional amendment in 2000. According to Article I, Section 4 of the United States Constitution, “the Times, Places and Manner of holding Elections for Senators and Representatives shall be prescribed in each State by the Legislature thereof.” The state legislature argued that the use of the word “legislature” in this context is literal; therefore, only a state legislature may draw congressional district lines. Meanwhile, the commission contended that the word “legislature” ought to be interpreted to mean “the legislative powers of the state,” including voter initiatives and referenda. On June 29, 2015, the court ruled 5-4 in favor of the Arizona Independent Redistricting Commission, finding that “redistricting is a legislative function, to be performed in accordance with the state’s prescriptions for lawmaking, which may include the referendum and the governor’s veto.” The majority opinion was penned by Justice Ruth Bader Ginsburg and joined by Justices Anthony KennedyStephen BreyerElena Kagan, and Sonia Sotomayor. Chief Justice John Roberts and Justices Clarence ThomasAntonin Scalia, and Samuel Alito dissented.[26][27][28][29]


See also: State-by-state redistricting procedures

Congressional redistricting

Most states are required to draw new congressional district lines every 10 years following completion of United States Census (those states comprising one congressional district are not required to redistrict). In 37 of these states, state legislatures were primarily responsible for redistricting as of November 2017. In four states, independent commissions drew congressional district lines. In two states, politician commissions drew the lines. The remaining states comprised one congressional district each, rendering redistricting unnecessary. See the map and table below for further details.[11][30]

State legislative redistricting

In 37 of the 50 states, state legislatures were primarily responsible for state legislative redistricting as of November 2017. Independent commissions drew state legislative district lines in six states. In seven states, politician commissions were responsible for state legislative redistricting. See the map and table below for further details.[11]


There are conflicting opinions regarding the correlation between partisan gerrymandering and electoral competitiveness. In 2012, Jennifer Clark, a political science professor at the University of Houston, said, “The redistricting process has important consequences for voters. In some states, incumbent legislators work together to protect their own seats, which produces less competition in the political system. Voters may feel as though they do not have a meaningful alternative to the incumbent legislator. Legislators who lack competition in their districts have less incentive to adhere to their constituents’ opinions.”[31]

In 2006, Emory University professor Alan Abramowitz and Ph.D. students Brad Alexander and Matthew Gunning wrote, “[Some] studies have concluded that redistricting has a neutral or positive effect on competition. … [It] is often the case that partisan redistricting has the effect of reducing the safety of incumbents, thereby making elections more competitive.”[32]

In 2011, James Cottrill, a professor of political science at Santa Clara University, published a study of the effect of non-legislative approaches (e.g., independent commissions, politician commissions) to redistricting on the competitiveness of congressional elections. Cottrill found that “particular types of [non-legislative approaches] encourage the appearance in congressional elections of experienced and well-financed challengers.” Cottrill cautioned, however, that non-legislative approaches “contribute neither to decreased vote percentages when incumbents win elections nor to a greater probability of their defeat.”[33]

Note: The electoral competitiveness data presented below is provided only for informational purposes. As noted above, there are conflicting opinions regarding the correlation between redistricting and competitiveness. A variety of factors at the local, state, and federal levels can impact electoral competitiveness.


See also: United States House of Representatives elections, 2016

In 2016, Ballotpedia analyzed the margins of victory in all contests for the United States House of Representatives.[34]Ballotpedia found that the average margin of victory was 36.81 percent. A total of 325 elections (74.03 percent of all House elections) were won by margins of victory of 20 percent or more. Sixteen elections (3.64 percent of all House elections) were won by margins of victory of less than 5 percent.

[hide]Electoral margins of victory in elections in 2016 United States House of Representatives elections
0%-5%5%-10%10%-20%20% or more
Number of elections161781325
Percentage of elections3.64%3.87%18.45%74.03%

State legislatures

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See also: Margin of victory in state legislative elections

In 2014, Ballotpedia conducted a study of competitive districts in 44 state legislative chambers between 2010, the last year in which district maps drawn after the 2000 census applied, and 2012, the first year in which district maps drawn after the 2010 census applied. Ballotpedia found that there were 61 fewer competitive general election contests in 2012 than in 2010. Of the 44 chambers studied, 25 experienced a net loss in the number of competitive elections. A total of 17 experienced a net increase. In total, 16.2 percent of the 3,842 legislative contests studied saw competitive general elections in 2010. In 2012, 14.6 percent of the contests studied saw competitive general elections. An election was considered competitive if it was won by a margin of victory of 5 percent or less. An election was considered mildly competitive if it was won by a margin of victory between 5 and 10 percent. For more information regarding this report, including methodology, see this article.

Majority-minority districts

Section 2 of the Voting Rights Act of 1965 mandates that electoral district lines cannot be drawn in such a manner as to “improperly dilute minorities’ voting power.”[35]

No voting qualification or prerequisite to voting, or standard, practice, or procedure shall be imposed or applied by any State or political subdivision to deny or abridge the right of any citizen of the United States to vote on account of race or color.[4]
—Voting Rights Act of 1965[36]

States and other political subdivisions may create majority-minority districts in order to comply with Section 2 of the Voting Rights Act.[37]

In 2015, there were 122 majority-minority districts spanning 26 states. California was home to 40 such districts, more than any other state.[38]

Support and opposition


Proponents of majority-minority districts argue that these districts are a necessary hindrance to the practice of cracking, which occurs when a constituency is divided between several districts in order to prevent it from achieving a majority in any one district. In an April 2015 report for the Congressional Research Service, legislative attorney L. Paige Whitaker described this argument as follows:[13]

A majority-minority district is one in which a racial or language minority group comprises a voting majority. The creation of such districts can avoid racial vote dilution by preventing the submergence of minority voters into the majority, which can deny minority voters the opportunity to elect a candidate of their choice.[4]
—L. Paige Whitaker

In addition, supporters argue that the drawing of majority-minority districts has resulted in an increased number of minority representatives in state legislatures and Congress. The American Civil Liberties Union, in a 2001 report, made this argument:[39][40][41][42]

In 1964, there were only about 300 black elected officials nationwide. By 1998 the number had grown to more than 8,858. This increase is the direct result of the increase in majority-minority districts since passage of the Voting Rights Act in 1965. … Given the persistent patterns of racial bloc voting in the South, the destruction of majority-minority districts, whether at the congressional or state and local levels, would inevitable lead to a decline in the number of minority office holders.[4]
American Civil Liberties Union


Critics, meanwhile, contend that the establishment of majority-minority districts can result in packing, which occurs when a constituency or voting group is placed within a single district, thereby minimizing its influence in other districts. Kim Soffen, writing for The Washington Post in June 2016, summarized this argument as follows:[43]

Imagine the minority-favored candidate can win an election in a district if at least 30 percent of voters are minorities. What harm is done by the legislators packing the district up to 50 percent minority voters? Much like political gerrymandering, it limits black influence in surrounding districts. It would require the creation of, for instance, a 50 percent and a 10 percent black district, rather than two 30 percent black districts. In other words, the requirement would give black voters one representative of their choice rather than two.[4]
—Kim Soffen

Because minority groups tend to vote Democratic, critics argue that majority-minority districts ultimately present an unfair advantage to Republicans by consolidating Democratic votes into a smaller number of districts. Steven Hill, writing for The Atlantic in June 2013, made the following argument:[39][40][41]

The drawing of majority-minority districts not only elected more minorities, it also had the effect of bleeding minority voters out of all the surrounding districts. Given that minority voters were the most reliably Democratic voters, that made all of the neighboring districts more Republican. The black, Latino, and Asian representatives mostly were replacing white Democrats, and the increase in minority representation was coming at the expense of electing fewer Democrats.[4]
—Steven Hill

Examples of Gerrymandering

North Carolina

Asheville’s woes are the story of America

Recent news

The link below is to the most recent stories in a Google news search for the terms Redistricting. These results are automatically generated from Google. Ballotpedia does not curate or endorse these articles.

See also

Select a state on the map below to read more about redistricting in that state.


External links



The lead curator for this post is Shuaib Ahmed.

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