How redistricting works

Explainer·Verified 2026-07-10

The answer

Every ten years, after the Census, the lines of every congressional and state legislative district get redrawn to keep populations roughly equal. Most people assume this is a neutral, technical process. It isn't. In most states, the same state legislature that runs for election under these maps is also the body that draws them. Only about 10 states use an independent commission for congressional maps, and mid-decade redistricting, redrawing lines between censuses, is rare but not against the rules everywhere. Texas did exactly that in 2025.

How it actually works

The Constitution requires a census every ten years, and Supreme Court rulings in 1964, Reynolds v. Sims and Wesberry v. Sanders, established that districts must have roughly equal populations, one person, one vote. After the 2020 Census, data was delivered to states in August 2021, delayed by COVID from an April deadline, kicking off the 2021-2022 redistricting cycle. The next cycle begins after the 2030 Census.¹

In most states, the legislature draws the new maps and the governor signs or vetoes them, the same political process as any other law. About 10 states use independent or primary commissions for congressional maps and around 15 use them for state legislative maps,² including Michigan, whose 13-member citizen commission, 4 Democrats, 4 Republicans, 5 independents, randomly selected from over 9,000 applicants, adopted new maps in December 2021 after being created by a 2018 ballot initiative that passed with 61.28% approval.³

Redistricting is supposed to happen once per decade, but in 2025 Texas redrew its congressional map mid-cycle after pressure from the White House to protect the GOP's narrow U.S. House majority ahead of the 2026 midterms. The legislature passed the new map in August 2025, aiming to shift the delegation from 25-13 to roughly 30-8 Republican. A federal panel blocked it in November 2025 as a racial gerrymander, but the Supreme Court stayed that ruling in December 2025, and the map stood for 2026. California, Missouri, and other states followed with their own mid-decade changes the same year.⁴

Who holds the power

In most states, the legislature and governor. In commission states, an independent or bipartisan panel, sometimes with legislative backup authority if the commission deadlocks. Courts, state and federal, can strike maps as illegal racial or, in some states, partisan gerrymanders (see gerrymandering-packing-and-cracking).

Where you come in

Find out whether your state uses a legislature or a commission to draw its maps. If your state doesn't have an independent commission, ballot initiatives are how several states, including Michigan, created one. See how-ballot-initiatives-work for that process.

Commission structures vary widely: some are fully independent, others are advisory only with the legislature retaining final say, and Iowa uses a distinct nonpartisan-staff-drawn process. Check your state's specific process, since "commission" doesn't always mean the same level of independence.

Glossary: redistricting-commission, majority-minority-district

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