How Gerrymandering Works—and Why It's Hard to Stop
Gerrymandering manipulates electoral district boundaries to lock in political power. Here's how packing, cracking, and modern technology shape American elections—and what reformers are trying to do about it.
A Word Born From a Salamander
In 1812, Massachusetts Governor Elbridge Gerry signed a bill that redrew the state's senate districts to benefit his Democratic-Republican Party. When a newspaper cartoonist noticed that one contorted Boston-area district resembled a salamander, the Boston Gazette published a now-famous illustration dubbing the creature a "Gerry-mander." The portmanteau stuck. More than two centuries later, gerrymandering remains one of the most powerful—and controversial—tools in American politics.
How Redistricting Creates the Opportunity
The U.S. Constitution requires a national census every ten years. Once new population counts arrive, each state must redraw the boundaries of its congressional and state legislative districts so that every district contains roughly the same number of people. This process is called redistricting.
Who draws the lines varies widely. In about 33 states, the state legislature controls congressional redistricting. Nine states use independent or bipartisan commissions, and a handful use hybrid systems. The remaining states have only one congressional seat, making redistricting unnecessary. Wherever elected officials control the pen, the temptation to draw maps that entrench their own power is enormous.
Packing and Cracking—the Two Core Tactics
Gerrymandering boils down to two complementary strategies:
- Packing: Concentrating opposition voters into as few districts as possible. Those districts produce lopsided victories for the minority party—but waste thousands of votes that cannot help win seats elsewhere.
- Cracking: Spreading the remaining opposition voters thinly across many districts so they never form a majority in any of them.
Used together, packing and cracking can let a party that wins, say, 50 percent of a state's votes claim 70 percent or more of its seats. The district map technically contains equal populations, yet the electoral playing field is dramatically tilted.
Technology Made It Worse
Before computers, gerrymandering was an imprecise art. Modern map-drawers use geographic information systems (GIS), voter-file databases, and high-speed computing to test thousands of possible maps in hours. Algorithms can optimize district lines down to the block level, sorting voters by party registration, race, income, and past turnout. The result is maps drawn with surgical precision—districts that look bizarre on paper but deliver reliable election outcomes for the party in charge.
What the Courts Have Said
The U.S. Supreme Court has drawn a sharp line between two types of gerrymandering. Racial gerrymandering—drawing districts to dilute minority voting power—violates the Voting Rights Act and the Equal Protection Clause, and courts regularly strike down such maps. Recent cases in Alabama, Louisiana, and South Carolina have all involved challenges to maps alleged to discriminate against Black voters.
Partisan gerrymandering is a different story. In the landmark 2019 case Rucho v. Common Cause, the Supreme Court ruled that federal courts cannot adjudicate claims of excessive partisan gerrymandering, calling it a "political question" beyond judicial reach. That decision pushed the fight to state courts and ballot initiatives, where reformers have had mixed success.
The Reform Movement
Seven states—Arizona, California, Colorado, Idaho, Michigan, Montana, and Washington—have created independent citizen-redistricting commissions designed to take map-drawing out of legislators' hands. These commissions typically include members from both major parties plus unaffiliated citizens, and they must follow criteria like compactness, contiguity, and preservation of communities of interest.
Yet reform is far from guaranteed. Ohio voters rejected a proposed independent commission in 2024, partly because of confusing ballot language. Virginia voters approved a bipartisan commission in 2020, only to see the legislature push a 2026 amendment that would temporarily reclaim map-drawing power. The tug-of-war between reform and retrenchment continues in statehouses across the country.
Why It Matters
Gerrymandering doesn't just determine which party wins—it shapes which kinds of candidates run. In safely drawn districts, the real contest is the primary election, not the general. That rewards ideological purists over moderates and contributes to the polarization that defines modern American politics. When voters cannot meaningfully choose their representatives, critics argue, representatives start choosing their voters instead.
