This principle is embodied in congressional redistricting, the drawing of district boundaries from which the people choose their representatives to the U.S. House of Representatives. Prior to the 1960s, court challenges to redistricting plans were considered non-justiciable political questions that were most appropriately addressed by the political branches of government, not the judiciary. In 1962, in the landmark ruling of Baker v. Carr , the Supreme Court pivoted and held that a constitutional challenge to a redistricting plan was not a political question and was justiciable. Since then, a series of constitutional and legal challenges have significantly shaped how congressional districts are drawn. For example, the Supreme Court recently clarified how a court should evaluate whether race was a predominant factor in the development of a redistricting plan when considering a Fourteenth Amendment equal protection claim. In April 2016, the Court ruled that states may draw their legislative districts based on total population rather than based on eligible or registered voters. In addition, as of the date of this report, two redistricting cases are currently pending before the Court: one case presents the question of whether partisanship can justify differences in population in the context of state legislative redistricting; another case presents the question of whether, in proving that race was a predominant factor in the creation of a redistricting plan, challengers must demonstrate that considerations of race predominated over politics. In order to comport with the constitutional standard of equality of population among districts, discussed below, at least once every 10 years, in response to changes in the number of Representatives apportioned to it or to shifts in its population, most states are required to draw new boundaries for its congressional districts. The Supreme Court has interpreted the Constitution to require that each congressional district within a state contain approximately the same population. This requirement is known as the "equality standard" or the principle of "one person, one vote." Specifically, Section 2 prohibits any voting qualification or practice—including congressional redistricting plans—applied or imposed by any state or political subdivision that results in the denial or abridgement of the right to vote based on race, color, or membership in a language minority. Under certain circumstances, the creation of one or more "majority-minority" districts may be required in a congressional redistricting plan. A majority-minority district is one in which a racial or language minority group comprises a voting majority. In order to facilitate determination of the totality of the circumstances, the Court listed the following factors, which originated in the legislative history accompanying enactment of Section 2: 
1. the extent of any history of official discrimination in the state or political subdivision that touched the right of the members of the minority group to register, to vote, or otherwise to participate in the democratic process;
2. the extent to which voting in the elections of the state or political subdivisions is racially polarized;
3. the extent to which the state or political subdivision has used unusually large election districts, majority vote requirements, anti-single shot provisions, or other voting practices or procedures that may enhance the opportunity for discrimination against the minority group;
4. if there is a candidate slating process, whether the members of the minority group have been denied access to that process;
5. the extent to which members of the minority group in the state or political subdivision bear the effects of discrimination in such areas as education, employment and health, which hinder their ability to participate effectively in the political process;
6. whether political campaigns have been characterized by overt or subtle racial appeals;
7. the extent to which members of the minority group have been elected to public office in the jurisdiction. In 2015, in Arizona State Legislature v. Arizona Independent Redistricting Commission , the Supreme Court upheld the constitutionality of an independent commission, established by initiative, for drawing congressional district boundaries. Conclusion

The legal framework for congressional redistricting resides at the intersection of the Constitution's limits and powers, requirements prescribed under federal law, and the various processes imposed by the states. Another recent Court decision construed the inoperable preclearance requirements in Section 5 of the Voting Rights Act to require a covered jurisdiction to maintain minority voters' ability to elect candidates of choice in a new redistricting plan, not to require that a particular numerical percentage of minority voters in a minority-majority district be maintained.
Congressional redistricting is the drawing of district boundaries from which the people choose their representatives to the U.S. House of Representatives. The legal framework for congressional redistricting resides at the intersection of the Constitution's limits and powers, requirements prescribed under federal law, and the various processes imposed by the states. Prior to the 1960s, court challenges to redistricting plans were considered non-justiciable political questions that were most appropriately addressed by the political branches of government, not the judiciary. In 1962, in the landmark ruling of Baker v. Carr, the Supreme Court pivoted and held that a constitutional challenge to a redistricting plan was not a political question and was justiciable. Since then, a series of constitutional and legal challenges have significantly shaped how congressional districts are drawn.
Key Takeaways from This Report
The Constitution requires that each congressional district contain approximately the same population. This equality standard was set forth by the Supreme Court in a series of cases articulating the principle of "one person, one vote." In order to comport with the equality standard, at least every 10 years, in response to changes in the number of Representatives or shifts in population, most states are required to draw new congressional district boundaries. Congressional districts are also required to comply with Section 2 of the Voting Rights Act (VRA), prohibiting any voting qualification or practice—including congressional redistricting plans—that results in the denial or abridgement of the right to vote based on race, color, or membership in a language minority. Under certain circumstances, the VRA may require the creation of one or more "majority-minority" districts, in which a racial or language minority group comprises a voting majority. However, if race is the predominant factor in the drawing of district lines, then a "strict scrutiny" standard of review applies. In 2015, in Alabama Legislative Black Caucus v. Alabama, the Supreme Court set forth standards for determining whether race is a predominant factor in creating a redistricting map when considering a Fourteenth Amendment equal protection claim. Alabama also held that the inoperable preclearance requirement in Section 5 of the VRA does not require that a new redistricting plan maintain the same percentage of minority voters in a majority-minority district. Instead, the Court held that Section 5 requires that the plan maintain a minority's ability to elect candidates of choice. Last year, in Arizona State Legislature v. Arizona Independent Redistricting Commission, the Court held that states can establish independent commissions, by ballot initiative, to conduct congressional redistricting. In April 2016, in Evenwel v. Abbott, the Court held that states may draw their legislative districts based on total population rather than based on eligible or registered voters. As of the date of this report, two redistricting cases are pending before the Supreme Court: Harris v. Arizona Independent Redistricting Commission, regarding whether partisanship can justify differences in population; and Wittman v. Personhuballah, regarding what challengers must demonstrate in proving that race was a predominant factor in the creation of a redistricting plan.