Judicial branch · Landmark case
Thornburg v. Gingles
478 U.S. 30 (1986) · Opinion of the Court
What you should know
This page explains the Court’s holding in plain language, where the official text lives, and what to check next.
Supreme Court findings are not news summaries. The controlling document is the Court’s opinion, plus any concurrences or dissents. Use this profile to understand the holding, then verify language, syllabus, and docket history on official sources before relying on a secondary account. The justices agreed unanimously on the outcome but split on some of the underlying legal reasoning — part of the opinion is a plurality, not a full majority.
The Court established the controlling three-part test for proving that an electoral district dilutes minority voting strength in violation of Section 2 of the Voting Rights Act: the minority group must be large and geographically compact enough to form a majority in a single-member district, the group must be politically cohesive, and the majority must usually vote as a bloc to defeat the minority’s preferred candidates. Applying that test, the Court upheld findings of illegal vote dilution in five of North Carolina’s multimember legislative districts, while reversing as to one district where Black candidates had found real, sustained electoral success.
Background
North Carolina’s 1982 legislative redistricting plan used several multimember districts — where voters elect multiple representatives from one shared district rather than one representative per single-member district. Black voters in six of these districts sued, arguing the multimember structure diluted their voting strength by combining them with a larger white voting bloc that would usually outvote their preferred candidates.
Congress had recently amended Section 2 of the Voting Rights Act to make clear that a vote-dilution claim only requires proving discriminatory effect, not discriminatory intent. The Court used this case to spell out exactly what proving that effect actually requires — the three-part “Gingles preconditions” that have governed vote-dilution litigation ever since.
The controlling test for vote dilution claims, cited in hundreds of redistricting cases since.
The “Gingles preconditions” remain the starting point any plaintiff must clear before a court will even consider whether a district’s overall circumstances add up to unlawful vote dilution — a framework still actively used in redistricting litigation across the country today.
Vote and authorship
| Opinion | Brennan, J. (unanimous as to judgment) |
|---|---|
| Plurality (Part III–C, racially polarized voting) | Brennan, joined by Marshall, Blackmun, Stevens |
| Dissent (in part) | None on the ultimate judgment; some justices disagreed with specific reasoning |
Where multimember districting generally works to dilute the minority vote, it cannot be defended on the ground that it sporadically and serendipitously benefits minority voters.
Justice Brennan · Thornburg v. Gingles
How it fits in government
Judicial branch
Established the operative legal test courts still use nationwide to evaluate vote-dilution claims under Section 2 of the Voting Rights Act.
State & local government
State legislatures draw the district lines and choose district structures (single-member vs. multimember) this ruling directly evaluates.
Voting Rights Act
This case is the Court’s central interpretation of Section 2’s amended “results test,” still cited in essentially every vote-dilution case decided since.
Official records visitors may need
SupremeCourt.gov
Opinions, docket search, rules, and Court information.
Oyez
Case abstract, oral argument audio, and justice votes.
Opinion text (FindLaw)
Readable public text of the case.
GovInfo · U.S. Courts
Official publications and related federal court materials.
Related research paths
Shaw v. Reno
A related but distinct racial-gerrymandering claim, decided under the Equal Protection Clause rather than Section 2.
Voting Rights Act of 1965
The federal law, and its Section 2 vote-dilution protections, at the center of this case.
Redistricting and multimember districts
How district structure itself can affect minority representation.
Landmark cases guide
Other holdings that define voting rights.