Redistricting and Gerrymandering

After each census, states with more than one House seat redraw their congressional districts, and every state redraws its legislative districts. In most states the legislature draws the maps, subject to the governor's veto. About a dozen states have shifted the job to commissions, some fully independent of elected officials, including California, Arizona, Colorado, and Michigan. The term gerrymander dates to 1812, when a Massachusetts district approved by Governor Elbridge Gerry was said to resemble a salamander.

Federal law sets two main constraints. Since Wesberry v. Sanders and Reynolds v. Sims in 1964, districts must have nearly equal populations, the principle of one person, one vote. Section 2 of the Voting Rights Act forbids maps that dilute the voting strength of racial minorities, which can require majority-minority districts, as the Supreme Court reaffirmed in Allen v. Milligan in 2023. But in Rucho v. Common Cause in 2019 the Court held that partisan gerrymandering claims are political questions beyond the reach of federal courts, leaving them to state courts, state constitutions, and Congress.

Mapping software and detailed voter data have made gerrymanders more precise, and both parties use them where they control the process. Redistricting normally happens once a decade, but in 2025 Texas redrew its map mid-decade at the President's urging to add Republican seats, and California voters responded by approving Proposition 50 to redraw its map in Democrats' favor, while several other states moved to follow. By the November 2026 midterms, new maps were in place in Texas, California, North Carolina, Ohio, Utah, Florida, Tennessee, and Louisiana, while Missouri's was suspended by a referendum, Virginia's was struck down by its supreme court, and Indiana's Senate rejected one. In April 2026, in Louisiana v. Callais, the Supreme Court limited when Section 2 of the Voting Rights Act can justify race-conscious districts.