Every ten years, following the decennial census, every state that sends more than one representative to Congress must draw new district maps. Those maps determine which voters live in which districts, which in turn shapes — sometimes decisively — which party is likely to win each seat. The process of drawing those maps is called redistricting, and it is one of the most consequential and least-discussed exercises of political power in American democracy.
Understanding who controls it, and what the rules governing it actually say, is necessary to understanding why some congressional delegations look nothing like the states they represent.
The Default: Legislative Control
In the majority of states, congressional maps are drawn by the state legislature and signed into law by the governor — essentially the same process used to pass any other legislation. This means that the party that controls the state legislature and the governorship at the time of redistricting has enormous power to shape maps in ways that advantage their candidates for the next decade.
The incentive to do so is obvious, and both parties have acted on it when they had the opportunity. After 2010, Republicans controlled the redistricting process in many of the largest states and used that control to draw maps that were subsequently found by analysts to have substantially increased their congressional advantage. After 2020, Democrats controlled the process in some states and drew maps that courts ultimately found violated state constitutional requirements.
Independent Commissions: The Reform Model
Fourteen states have created some form of independent or bipartisan redistricting commission to draw congressional maps, though the structures vary considerably. California's commission, created by ballot initiative in 2008, is composed of 14 citizens chosen through a multi-stage application and screening process designed to exclude current and former politicians and their immediate family members. Arizona's commission includes five members, with the legislative leaders of each party each appointing two and those four agreeing on a fifth.
The performance of these commissions has been mixed. California's has generally produced maps that independent analysts have rated as more competitive and less skewed than legislatively drawn maps in comparable states. Arizona's has been mired in legal challenges and political disputes, with the Arizona legislature repeatedly attempting to assert control over the commission's work.
"The problem with redistricting reform is that any process that produces genuinely fair maps will produce maps that one party or the other finds unacceptable. Neutrality in a system that hasn't been neutral is itself a form of disruption."
What the Courts Have Said
The Supreme Court's 2019 ruling in Rucho v. Common Cause was a significant setback for reformers. The Court held, 5-4, that federal courts have no role in adjudicating partisan gerrymandering claims — that the question of whether a map is drawn to advantage one party is a political question beyond the reach of federal judicial review.
That ruling did not foreclose all legal challenges. State courts applying state constitutional provisions have struck down several maps drawn after 2020. North Carolina's state Supreme Court initially struck down a Republican-drawn map as a violation of the state constitution, then reversed course after the court's composition changed following the 2022 elections — a sequence that illustrated precisely the limits of judicial solutions to redistricting.
Racial gerrymandering — drawing maps to dilute the voting power of racial minorities — remains subject to federal challenge under the Voting Rights Act and the Fourteenth Amendment. The Supreme Court has continued to enforce the Voting Rights Act's prohibition on racial vote dilution, even as it has declined to engage with partisan claims, and several maps have been redrawn following successful racial gerrymandering challenges.
The Criteria That Matter
Maps are typically evaluated against several criteria: compactness (districts should not have bizarre shapes), contiguity (all parts of a district should be connected), preservation of political subdivisions (districts should not unnecessarily split counties or municipalities), and population equality (all districts in a state must have nearly identical populations). Some states add requirements for competitive districts or proportional representation of minority communities.
The problem is that these criteria often conflict, and the choices made when criteria conflict are themselves political. A compact district in a city might pack Democratic voters together in ways that make surrounding suburban districts safer for Republicans. A district drawn to comply with the Voting Rights Act by creating a majority-minority district might, as a side effect, make neighboring districts whiter and more Republican.
A Federal Solution?
Congressional Democrats have twice passed the For the People Act, which would require all states to use independent commissions for congressional redistricting and establish national criteria for map-drawing. Both times, the bill failed in the Senate, blocked by a filibuster that has itself become a subject of the redistricting-adjacent debate about democratic reform.
Whether federal legislation is constitutionally permissible is a question with a clear answer — Article I, Section 4 explicitly gives Congress the authority to regulate the manner of congressional elections — but whether it is politically achievable in the current environment is a separate question, and the answer there is considerably less clear.