How Congressional Redistricting Works

Congressional districts are redrawn after the decennial census so districts within a state have roughly equal populations. States use different institutions and procedures to draw the lines.

Redistricting can generate lawsuits involving constitutional requirements, federal voting-rights law and state-law rules. Courts may allow, block or require changes to maps depending on the claims and timing.

Late map changes can create practical problems for candidate filings, primary elections, ballot preparation and voter education.