- Gerrymandering uses two core techniques: packing (concentrate opponents into few districts, wasting their votes) and cracking (split opponents across many districts so they never form a majority) — used together, a party can win 60% of seats with only 45% of the statewide vote
- In 2019, the Supreme Court ruled 5-4 in Rucho v. Common Cause that federal courts cannot review partisan gerrymandering claims — state courts are the only remaining avenue for challenge
- Maps drawn after the 2020 census will govern elections through 2030; Texas and Florida gained seats while New York and Illinois lost them, shifting the partisan baseline for the 2026 House races
- More than 20 states use some form of independent redistricting commission — but "independent" varies widely; gerrymandering is a key structural factor in why the generic ballot gap between votes and seats can be so large
Packing and Cracking: The Core Techniques
Packing
Packing concentrates the opposing party's voters into as few districts as possible. The packed party wins those districts by massive margins — 80%, 90%, even more — but all those "excess" votes beyond what is needed to win are wasted. A party that wins one seat 90-10 has wasted 40 points of margin that could have helped them in neighboring districts. Packing is how you turn a geographic concentration of the opposition into a liability for them.
Cracking
Cracking splits the opposing party's voters across multiple districts so they never constitute a majority in any of them. A city that might form a natural district voting 65% Democratic can be split into three districts, each containing one-third of the city surrounded by two-thirds rural Republican territory. The urban Democratic voters are diluted below majority in all three districts. Combined with packing, cracking is how map-drawers can turn a 45-55 statewide partisan split into a 3-to-7 seat disadvantage.
Partisan vs. Racial Gerrymandering
American courts treat partisan and racial gerrymandering very differently, even though in practice they often overlap.
Racial Gerrymandering: Legally Limited
The Voting Rights Act of 1965 and the 14th Amendment's Equal Protection Clause impose real constraints on racial gerrymandering. States cannot draw district lines primarily based on race — this is called "racial packing" and violates the Constitution. At the same time, the VRA requires that minority communities have sufficient voting power to elect representatives of their choice in some circumstances — which can require creating majority-minority districts.
This tension is the subject of ongoing litigation. In Allen v. Milligan (2023), the Supreme Court upheld Section 2 of the Voting Rights Act and ordered Alabama to draw a second Black-majority congressional district after finding the state had diluted Black voting power. Chief Justice Roberts joined the three liberal justices and Justice Kavanaugh in the 5-4 ruling — a significant check on racial gerrymandering.
Partisan Gerrymandering: Federal Courts Out
Partisan gerrymandering — drawing maps to advantage one political party — has been far harder to challenge legally. In 2019, the Supreme Court ruled 5-4 in Rucho v. Common Cause that partisan gerrymandering claims present a "political question" beyond the reach of federal courts. Chief Justice Roberts wrote for the majority that while extreme partisan gerrymandering may be "unjust" and "incompatible with democratic principles," federal courts have no manageable standard to review it.
This does not mean partisan gerrymanders are immune from legal challenge everywhere. State courts can review partisan gerrymanders under state constitutions — and several have. North Carolina's state supreme court struck down Republican congressional maps in 2022, then the court's partisan composition changed and it reversed course in 2023. Pennsylvania, Ohio, and New York state courts have all weighed in on redistricting with varying outcomes.
Notable Gerrymandering Cases and Examples
| State / Case | Type | What Happened | Outcome |
|---|---|---|---|
| Rucho v. Common Cause (NC/MD) | Partisan | NC Republicans drew 10-3 R map; MD Democrats drew 7-1 D map | SCOTUS: federal courts cannot review partisan gerrymandering (2019) |
| Allen v. Milligan (AL) | Racial/VRA | Alabama had 27% Black population but only 1 of 7 majority-Black districts | SCOTUS ordered second majority-Black district (2023, 5-4) |
| Wisconsin (2012–2018) | Partisan | Rs won 60 of 99 Assembly seats with 48.6% of vote in 2012 | Gill v. Whitford dismissed on standing (SCOTUS 2018) |
| Ohio (2020 cycle) | Partisan | Republican-drawn maps struck down 7 times by Ohio Supreme Court | Maps used anyway after court composition changed; federal courts declined jurisdiction |
| New York (2022) | Partisan | Democratic legislature drew extreme D-favoring maps | NY Court of Appeals struck down as violating state constitution; independent maps drawn |
Independent Redistricting Commissions
The most common reform proposal is to remove redistricting from partisan legislatures and give it to an independent commission. These exist in various forms in more than 20 states, though the degree of actual independence varies enormously.
California's Citizens Redistricting Commission (established 2008) is often cited as a model. Members are selected through a multi-step screening process to exclude current and recent politicians, political consultants, and major donors. The commission draws both congressional and state legislative maps. A 2019 Harvard study found California's maps were among the least partisan in the country.
Arizona's Independent Redistricting Commission (established 2000 by ballot initiative) was challenged by the Republican-controlled state legislature as unconstitutional. The Supreme Court upheld the commission 5-4 in Arizona State Legislature v. Arizona Independent Redistricting Commission (2015), ruling that "legislature" in the Elections Clause means the state's entire lawmaking process, including ballot initiatives.
Michigan created an independent commission by ballot initiative in 2018 that drew the 2020-cycle maps. The Michigan Citizens Redistricting Commission is prohibited from including politicians, lobbyists, or party officers. Its maps significantly reduced the partisan bias of Michigan's congressional delegation — a key factor in the competitiveness of Michigan's 2026 Senate race.
Not all commissions are equally independent. Several states use "bipartisan" commissions equally split between Republicans and Democrats with a tiebreaker — these can still produce gerrymandered maps if both parties agree to protect incumbents at the expense of competitive seats.
Frequently Asked Questions
What is gerrymandering?
Gerrymandering is the manipulation of electoral district boundaries to advantage one party or group. By controlling where district lines are drawn, the party in power can choose which voters are in which districts — effectively choosing their voters before voters choose them. The term comes from Massachusetts Governor Elbridge Gerry, who in 1812 signed a state senate district shaped like a salamander designed to protect his party.
What is the difference between packing and cracking?
Packing concentrates opponents into a few districts so they win big there but waste votes. Cracking divides opponents across many districts so they are diluted below a majority in each. Used together, these techniques allow a party to win most seats with a minority of total votes — for example, winning 60% of congressional seats with only 45% of the statewide vote.
Is partisan gerrymandering illegal?
Not at the federal level. In Rucho v. Common Cause (2019), the Supreme Court held 5-4 that federal courts cannot review partisan gerrymandering claims. However, state courts can still strike down maps under state constitutions — and several have. Racial gerrymandering remains subject to federal review under the Voting Rights Act and the 14th Amendment.
What is an independent redistricting commission?
An independent redistricting commission draws district maps outside the partisan legislature. California, Arizona, Michigan, and Colorado are among states with commissions. The Supreme Court upheld voter-created commissions as constitutional in 2015. True independence varies: some commissions exclude politicians and donors (California model), while "bipartisan" commissions split evenly between parties can still produce self-serving maps.
