Gerrymandering: packing and cracking
The answer
Gerrymandering isn't just drawing weird-shaped districts. It's a set of two specific techniques for turning a group of voters' numbers against them. Packing crowds opposition voters into a small number of districts so they win those by huge, wasted margins. Cracking spreads them thin across many districts so they never reach a majority anywhere. Most people assume unfair maps are illegal. For partisan gerrymandering, since a 2019 Supreme Court ruling, they usually aren't, at least not in federal court.
How it actually works
Map-drawers who control the process can use census block-level data to sort voters with surgical precision. Pack the opposition's voters into a few overwhelmingly one-sided districts, and their votes are wasted on landslide wins. Crack the rest across many districts where they're a minority in each one, and their influence is neutralized everywhere else.1 Brennan Center's 2024 analysis found this produced a net 16-seat Republican advantage in the U.S. House nationally that year, with only 27 districts decided by less than 5 points.2
Courts still police racial gerrymandering aggressively. In April 2026, the Supreme Court ruled 6-3 in Louisiana v. Callais that Louisiana's second Black-majority congressional district, itself created to remedy an earlier Voting Rights Act violation, was an unconstitutional racial gerrymander. The ruling also narrowed the legal framework courts have used since 1986 to evaluate Voting Rights Act vote-dilution claims, making future claims harder to bring, and forced Louisiana to suspend its May 2026 primary while it redraws the map (see primary-systems-explained for Louisiana's broader 2026 primary overhaul).3
Partisan gerrymandering is a different story. In Rucho v. Common Cause (2019), the Supreme Court ruled 5-4 that federal courts have no role in policing partisan gerrymanders at all, calling it a political question outside their jurisdiction. That pushed partisan-gerrymandering fights into state courts under state constitutions, with inconsistent results: Wisconsin's state supreme court effectively ended one of the country's most extreme partisan gerrymanders in a 2023 ruling, while North Carolina's top court ruled the same year that its own state constitution doesn't allow such claims either.4
Who holds the power
Whoever draws the map, usually the state legislature (see how-redistricting-works), and secondarily the courts, state or federal, that decide whether a given map crosses a legal line. Since Rucho, that line is drawn very differently depending on which state's courts you're in.
Where you come in
Racial gerrymandering claims can still go to federal court. Partisan gerrymandering claims depend entirely on your state's constitution and courts, so know which kind of challenge is even available where you live before assuming a map can be challenged at all. Because Rucho pushed partisan claims to the states, the legal landscape is genuinely inconsistent, check your specific state's redistricting litigation history rather than assuming a national standard applies.
Related
Glossary: gerrymander, packing, cracking, majority-minority-district, safe-seat
See also: how-redistricting-works