A gerrymandering case’s path depends almost entirely on what kind of unfairness the plaintiffs are alleging. Understanding how gerrymandering cases work starts with that split: racial gerrymandering claims proceed in federal court under the Fourteenth Amendment or the Voting Rights Act, while partisan gerrymandering claims — closed out of federal court by the Supreme Court in 2019 — now live or die in state courts under state constitutions. From there, the case turns on standing, a mountain of statistical evidence, a tight election calendar, and, if plaintiffs win, a scramble to produce a lawful replacement map.
The Two Federal Tracks for Racial Claims
Racial gerrymandering challenges run on two tracks that pull in opposite directions, and states have to thread the needle between them.
The first track comes from the Equal Protection Clause. In Shaw v. Reno (1993), the Supreme Court held that when race is the predominant factor in drawing district lines, courts apply strict scrutiny.1Justia. Shaw v. Reno, 509 US 630 (1993) The state then has to prove the map serves a compelling interest and is narrowly tailored to achieve it.2Constitution Annotated. Amdt14 S1 8.6.6 Racial Vote Dilution and Racial Gerrymandering A bizarrely shaped district that can’t be explained by anything other than race can trigger that analysis without direct evidence of intent. The real fight is usually whether race drove line-drawing more than traditional criteria like keeping communities whole, following county lines, and keeping shapes compact.
The second track comes from Section 2 of the Voting Rights Act, codified at 52 U.S.C. § 10301, which bans any voting practice that leaves minority voters with less opportunity to elect their preferred candidates.3Office of the Law Revision Counsel. 52 Code 10301 – Denial or Abridgement of Right to Vote on Account of Race or Color Section 2 is a results test. Plaintiffs don’t have to prove discriminatory intent; they have to prove discriminatory effect, using the framework from Thornburg v. Gingles (1986). Three preconditions:
- The minority group is large enough and geographically compact enough to form a majority in a reasonably drawn district.
- The minority group is politically cohesive.
- The white majority votes as a bloc that usually defeats the minority group’s preferred candidates.4Justia. Thornburg v. Gingles, 478 US 30 (1986)
Clearing all three preconditions only gets plaintiffs to the next step. The court then looks at the totality of the circumstances — the jurisdiction’s history of discrimination, whether campaigns have used racial appeals, how often minority candidates have won — before deciding whether Section 2 has been violated.
Those two tracks collide in practice. The Supreme Court reaffirmed Gingles in Allen v. Milligan (2023), finding that Alabama’s congressional map likely violated Section 2 by not including an additional majority-Black district.5Supreme Court of the United States. Allen v. Milligan Two years later, in Louisiana v. Callais (2025), the Court struck down a remedial congressional map as an unconstitutional racial gerrymander, finding that the Voting Rights Act had not actually required the state to draw the additional majority-minority district it drew.6Supreme Court of the United States. Louisiana v. Callais Draw too few majority-minority districts, risk a Section 2 suit. Draw too many with race as the predominant factor, risk an Equal Protection suit.
Partisan Claims After Rucho
Federal courts are closed to gerrymandering claims based on partisan unfairness alone. In Rucho v. Common Cause (2019), the Supreme Court held that partisan gerrymandering presents a political question federal judges have no manageable standard to resolve, and said federal courts “have no license to reallocate political power between the two major political parties.”7Supreme Court of the United States. Rucho v. Common Cause The Constitution, the Court said, doesn’t require proportional representation, and there’s no principled line between acceptable partisanship and unconstitutional manipulation.8Constitution Annotated. ArtIII S2 C1 9.11 Nonjusticiability of Partisan Gerrymandering Claims
Rucho shifted the fight, not ended it. State constitutions often contain “free and fair elections” clauses with broader protections than the federal Constitution offers, and state supreme courts in Pennsylvania and North Carolina, among others, have used them to strike down partisan maps. For anyone considering a partisan challenge today, the venue is almost always state court, and the strength of the claim depends on the specific wording of that state’s constitution.
Who Can Sue
A plaintiff needs a concrete, personal injury — not a general objection to unfair politics. In redistricting, that usually means showing the district you personally live in was drawn to dilute your vote or to sort you by race.9Congressional Research Service. Partisan Gerrymandering: Supreme Court Provides Guidance on Standing and Maintains Legal Status Quo Statewide complaints that voters of a particular party were harmed, without identifying injured voters in specific districts, aren’t enough. That district-by-district rule shapes how cases are built: organizations like the NAACP or Common Cause typically recruit named plaintiffs who actually live in the challenged districts and pair them with institutional legal resources.
How Plaintiffs Build the Case
Redistricting cases are among the most data-intensive in American law. The fight is really over expert reports, and most of it happens long before trial.
Census Data
Every case starts with the P.L. 94-171 redistricting data the Census Bureau delivers to each state within a year of each decennial census.10U.S. Census Bureau. Decennial Census P.L. 94-171 Redistricting Data Summary Files It breaks population down by race, ethnicity, and voting age at the census-block level. That’s what plaintiffs use to show a minority group is big enough and compact enough to anchor a properly drawn majority-minority district — the first Gingles precondition.
Racially Polarized Voting
The second and third Gingles preconditions require statistical proof. Because ballots are secret, analysts estimate individual voting behavior from precinct-level results using methods like homogeneous precinct analysis, ecological regression, and ecological inference. Expert witnesses pair those estimates with American Community Survey data on citizen voting-age population, since only citizens over eighteen can vote.
Compactness
Shape matters. Courts use mathematical measures — most commonly the Polsby-Popper score (comparing district area to a circle of the same perimeter) and the Reock score (comparing it to the smallest enclosing circle) — to flag districts whose geography is hard to justify. Both produce a value between 0 and 1; higher means more compact. A low score doesn’t win a case on its own, but it invites a court to ask why the lines ended up where they did.
The Efficiency Gap
Partisan cases in state court often rely on the efficiency gap, which counts “wasted” votes — votes cast for a losing candidate or for a winner beyond the margin needed to win. Cracking (splitting a group across districts so it loses everywhere) and packing (concentrating it in a few districts where it wins by overwhelming margins) both inflate wasted votes for the targeted party. A large gap suggests one party converted votes into seats far more efficiently than the other.
Experts
Mathematicians, political scientists, demographers, and GIS specialists turn the raw data into reports and testimony. Their job is to show the map deviates meaningfully from what a neutral process would produce, and that the deviation didn’t happen by accident. Hourly rates for redistricting experts commonly run from about $200 to $350, and a single cycle’s expert costs can reach into the hundreds of thousands of dollars.
The Procedural Path
Three-Judge Panels and Direct Supreme Court Appeal
Federal constitutional challenges to congressional or legislative apportionment don’t go to a single district judge. They go to a three-judge district court: the judge who gets the filing, plus two more designated by the chief judge of the circuit, at least one of whom must be a circuit judge.11Office of the Law Revision Counsel. 28 Code 2284 – Three-Judge Court; When Required; Composition; Procedure Appeals from those panels skip the circuit courts of appeals entirely and go straight to the Supreme Court.12Office of the Law Revision Counsel. 28 Code 1253 – Direct Appeals From Decisions of Three-Judge Courts That shortcut is why so many redistricting disputes end up on the Supreme Court’s docket.
State Court Cases
State court cases follow the ordinary path: trial court, intermediate appellate court, state supreme court. They draw less national attention but have produced some of the most forceful recent interventions, in part because state constitutional protections for fair elections can give state judges more room to act than federal judges have.
Discovery and Trial
Discovery is often where cases are decided. Plaintiffs subpoena internal communications from legislators and the consultants they hired, looking for emails, texts, and meeting notes showing why specific lines were drawn where they were. Depositions of the mapmakers and political operatives add another layer. At trial, both sides present proposed maps, expert analyses, and documentary evidence, and the court applies the governing standard — strict scrutiny for Equal Protection claims, the Gingles framework for Section 2, or the applicable state constitutional test for partisan claims.
The Election Calendar: The Purcell Principle
Timing can beat a strong case. In Purcell v. Gonzalez (2006), the Supreme Court said courts should avoid changing election rules or maps close to an election because last-minute changes risk confusing voters and election administrators.13Justia. Purcell v. Gonzalez, 549 US 1 (2006) The Court has never defined “close,” but it has reversed lower court orders issued only weeks before Election Day.
The practical result: courts sometimes let an election proceed under a map they’ve already said is likely unlawful, pushing the remedy to the next cycle. File too early and the case may not be ripe; file too late and the court may refuse to act in time to matter. Experienced litigators treat the election calendar as the single most important variable in planning a case.
What Happens If a Map Is Struck Down
The Legislature Goes First
When a court invalidates a map, it typically gives the legislature a tight window, often just weeks, to draw a replacement that fixes the identified defects. Elections run on fixed schedules, and ballots, filing deadlines, and voter registration all depend on knowing where the lines are. A remedial map that reshuffles the same problems will be rejected.
Court-Drawn Maps
If the legislature deadlocks or produces another defective map, the court takes over. Federal courts usually appoint a special master — often a law professor or retired judge — who works with cartographers using the same census data and criteria at issue in the case. In recent Alabama litigation, the special master drew boundaries without using racial population data in the initial drafting, then checked effectiveness with past election results, evaluated compactness with Polsby-Popper and Reock scores, and measured how much of each existing district’s population was retained. State courts do something similar, sometimes using a special referee instead. Parties get a chance to submit their own maps and comment on the special master’s draft before the court adopts a final plan. That remedial map stays in effect until the next decennial redistricting cycle unless the legislature replaces it with a valid one or another challenge succeeds.
Independent Redistricting Commissions
Some states have moved mapmaking out of the legislature entirely. After the 2020 census, independent redistricting commissions had primary responsibility for drawing congressional districts in 11 of the 44 states with multiple House seats.14Congressional Research Service. Redistricting Commissions for Congressional Districts Commission structures vary, from independent panels built through a mix of judicial selection and random lot to advisory bodies the legislature can override. Commission maps are not immune from suit — they can still be challenged under Section 2 or the Equal Protection Clause — but removing the most obvious partisan incentives tends to narrow the fights that do arise.