The Constitution requires a count of the U.S. population every 10 years. Based on the census, the number of seats in the House of Representatives is reapportioned among the states. Thus, at least every 10 years, in response to changes in the number of Representatives apportioned to it or to shifts in its population, each state is required to draw new boundaries for its congressional districts. Although each state has its own process for redistricting, congressional districts must conform to a number of constitutional and federal statutory standards, including the Voting Rights Act (VRA) of 1965. The VRA was enacted under Congress's authority to enforce the 15 th Amendment, which provides that the right of citizens to vote shall not be denied or abridged on account of race, color, or previous servitude. In a series of cases and evolving jurisprudence, the U.S. Supreme Court has interpreted how the VRA applies in the context of congressional redistricting. These decisions inform how congressional district boundaries are drawn, and whether legal challenges to such redistricting plans will be successful. This report provides a legal overview of Section 2 of the VRA, a key provision affecting congressional redistricting, and selected Supreme Court case law. It discusses Sections 4 and 5, and the recent Supreme Court decision holding Section 4(b) unconstitutional, Shelby County v. Holder . Section 4 contained a coverage formula that identified states and jurisdictions that were required to gain federal approval or "preclearance" to proposed redistricting plans under Section 5. The report also provides an overview of selected legislation in the 113 th and 114 th Congresses that would establish additional requirements and standards for congressional redistricting, and amend the VRA to, among other things, reinstitute a coverage formula for Section 5 preclearance. Congressional district boundaries in every state are required to comply with Section 2 of the VRA. Section 2 provides a right of action for private citizens or the government to challenge discriminatory voting practices or procedures, including minority vote dilution, the diminishing or weakening of minority voting power. Specifically, Section 2 prohibits any voting qualification or practice—including the drawing of 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. The statute further provides that a violation is established if: based on the totality of circumstances, it is shown that the political processes leading to nomination or election in the State or political subdivision are not equally open to participation by [members of a racial or language minority group] in that its members have less opportunity than other members of the electorate to participate in the political processes and to elect representatives of their choice. 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. 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. In the landmark decision Thornburg v. Gingles , the Supreme Court established a three-prong test that plaintiffs claiming vote dilution under Section 2 must prove: First, the minority group must be able to demonstrate that it is sufficiently large and geographically compact to constitute a majority in a single-member district.... Second, the minority group must be able to show that it is politically cohesive.... Third, the minority must be able to demonstrate that the white majority votes sufficiently as a bloc to enable it—in the absence of special circumstances, such as the minority candidate running unopposed—usually to defeat the minority's preferred candidate. The Court also discussed how, under Section 2, a violation is established if based on the "totality of the circumstances" and "as a result of the challenged practice or structure plaintiffs do not have an equal opportunity to participate in the political processes and to elect candidates of their choice." 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. Further interpreting the Gingles three-prong test, in Bartlett v. Strickland , the Supreme Court ruled that the first prong of the test—requiring geographical compactness sufficient to constitute a majority in a district—can only be satisfied if the minority group constitutes more than 50% of the voting population if it were in a single-member district. In Bartlett , it had been argued that Section 2 requires drawing district lines in such a manner to allow minority voters to join with other voters to elect the minority group's preferred candidate, even where the minority group in a given district comprises less than 50% of the voting age population. Rejecting that argument, the Court found that Section 2 does not grant special protection to minority groups that need to form political coalitions in order to elect candidates of their choice. To mandate recognition of Section 2 claims where the ability of a minority group to elect candidates of choice relies upon "crossover" majority voters would result in "serious tension" with the third prong of the Gingles test. The third prong of Gingles requires that the minority be able to demonstrate that the majority votes sufficiently as a bloc to enable it usually to defeat minority-preferred candidates. Congressional redistricting plans must also conform with standards of equal protection under the 14 th Amendment to the U.S. Constitution. According to the Supreme Court, if race is the predominant factor in the drawing of district lines, above other traditional redistricting considerations—including compactness, contiguity, and respect for political subdivision lines—then a "strict scrutiny" standard of review is applied. In this context, strict scrutiny review requires that a court determine that the state has a compelling governmental interest in creating a majority-minority district, and that the redistricting plan is narrowly tailored to further that compelling interest. Case law in this area demonstrates a tension between compliance with the VRA and conformance with standards of equal protection. In Easley v. Cromartie (Cromartie II) , the Supreme Court upheld the constitutionality of the long-disputed 12 th Congressional District of North Carolina against the argument that the 47% black district was an unconstitutional racial gerrymander. In this case, North Carolina and a group of African American voters had appealed a lower court decision holding that the district, as redrawn by the legislature in 1997 in an attempt to cure an earlier violation, was still unconstitutional. The Court determined that the basic question presented in Cromartie II was whether the legislature drew the district boundaries "because of race rather than because of political behavior (coupled with traditional, nonracial redistricting considerations)." In applying its earlier precedents, the Court determined that the party attacking the legislature's plan had the burden of proving that racial considerations are "dominant and controlling." Overturning the lower court ruling, the Supreme Court held that the attacking party did not successfully demonstrate that race, instead of politics, predominantly accounted for the way the plan was drawn. In a recent case, Alabama Legislative Black Caucus v. Alabama , the Court clarified that in determining whether race is a predominant factor in the redistricting process, a court must engage in a district-by-district analysis instead of analyzing the state as an undifferentiated whole. It further confirmed that in calculating the predominance of race, a court is required to determine whether the legislature subordinated traditional race-neutral redistricting principles to racial considerations. The "background rule" of equal population, however, is not a traditional redistricting principle and therefore should not be weighed against the use of race to determine predominance, the Court held. In other words, the Court explained, if 1,000 additional voters need to be moved to a particular district in order to achieve equal population, ascertaining the predominance of race involves examining which voters were moved, and whether the legislature relied on race instead of other traditional factors in making those decisions. In Shelby County v. Holder the U.S. Supreme Court invalidated Section 4(b) of the VRA. Section 4(b) contained a formula prescribing which states and jurisdictions with a history of discrimination were required to obtain federal approval or "preclearance" under Section 5 before changing any voting law, including redistricting plans. Section 5 and the Court's ruling in Shelby County are discussed below. As a result of the Court's decision, the nine states, and jurisdictions within six states, that were previously covered under the formula are no longer subject to the VRA's preclearance requirement. The covered states were Alabama, Alaska, Arizona, Georgia, Louisiana, Mississippi, South Carolina, Texas, and Virginia. The six states containing covered jurisdictions were California, Florida, Michigan, New York, North Carolina, and South Dakota.