Thornburg v. Gingles (1986)

In 1982 Congress amended Section 2 of the Voting Rights Act so that plaintiffs could prove a violation by showing discriminatory results, without proving discriminatory intent. Black voters in North Carolina challenged the state's 1982 legislative plan, which used large multimember districts in which white majorities could elect every seat, arguing that the design diluted Black voting strength.

On June 30, 1986, the Supreme Court largely upheld a lower court ruling for the voters, in an opinion by Justice William Brennan. The Court set out three preconditions for a vote dilution claim: the minority group must be large and geographically compact enough to form a majority in a district, it must be politically cohesive, and the white majority must usually vote as a bloc to defeat the minority's preferred candidates. If those conditions are met, courts then weigh the totality of circumstances, including the history of discrimination.

The Gingles framework guided redistricting for four decades and led to the creation of many majority-minority districts, especially after the 1990 census. The Court reaffirmed it in Allen v. Milligan in 2023, but in Louisiana v. Callais in 2026 it updated the framework and limited when Section 2 can justify drawing districts based on race. Supporters credit Gingles with greatly increasing minority representation in Congress and state legislatures, while critics argue it encouraged race-based districting.