What Is Gerrymandering? A Plain-Language Definition

Gerrymandering is the deliberate manipulation of electoral district boundaries to give one political party or group an unfair advantage in elections. Instead of letting voters decide who wins, politicians choose their voters by drawing lines that either concentrate or scatter their opponents' supporters. The term dates back to 1812, when Massachusetts Governor Elbridge Gerry signed a redistricting plan that created a salamander-shaped district—hence "Gerry-mander."

At its core, gerrymandering undermines the principle of one person, one vote. When districts are drawn fairly, each vote carries roughly equal weight. Gerrymandering tips the scales, allowing a party with minority support to secure a majority of seats. This practice is legal in most U.S. states, though courts have repeatedly struck down maps found to be extreme or racially discriminatory.

A Brief History of Gerrymandering in the United States

While the term was coined in 1812, the practice existed long before. The earliest redistricting battles occurred soon after the Constitution required seats in the House of Representatives to be apportioned by population. In the 18th century, party leaders in states like Virginia and Pennsylvania already understood that district shapes could decide elections.

Throughout the 19th and 20th centuries, gerrymandering evolved alongside demographic shifts and legal rulings. The "rotten boroughs" of England—districts that persisted with few voters while others had many—inspired U.S. reformers to push for periodic redistricting. But until the 1960s, many states simply failed to redraw boundaries for decades, giving rural areas disproportionate power over growing cities.

Key Supreme Court cases changed the landscape. In Baker v. Carr (1962) and Reynolds v. Sims (1964), the Court established the principle of "one person, one vote," requiring districts to have roughly equal populations. Yet the Court did not ban partisan gerrymandering outright, leaving the door open for sophisticated map manipulation.

Methods of Gerrymandering: The Playbook

Cracking

Cracking spreads a group of voters—often a racial minority or supporters of the opposing party—across multiple districts. In each district, that group becomes a minority, unable to elect its preferred candidate. For example, if a city's Democratic voters are concentrated in a few neighborhoods, a Republican-controlled legislature might split those neighborhoods into several suburban districts, ensuring each is majority Republican.

Packing

Packing does the opposite: it squeezes as many opposition voters as possible into a single district. That district becomes a "safe seat" for the opposition, but the surrounding districts become safer for the party drawing the map. The overall result is that the packing party wins far more seats than its share of the statewide vote would suggest.

Hijacking and Kidnapping

Two less common but equally aggressive techniques target incumbents directly. Hijacking redraws district lines to pit two incumbents from the same party against each other in a primary, forcing one out. Kidnapping moves a popular incumbent's home into a different district—often one that is heavily opposed to that official—making reelection nearly impossible. These tactics are especially common during mid-decade redistricting, when the dominant party can fine-tune maps.

Stacking and Splitting Precincts

Beyond the big four, mapmakers use stacking (placing disparate groups together to create a majority for one party) and splitting precincts at the finest possible level to fine-tune partisan outcomes. Modern geospatial software allows cartographers to identify individual blocks and even households, making precision gerrymandering easier than ever.

The Impact of Gerrymandering on Democracy

Less Competitive Elections

When districts are carefully engineered to be safe for one party, general elections become foregone conclusions. In 2020, fewer than 10% of U.S. House districts were considered competitive. Most incumbents face no serious challenge from the other party, reducing accountability and encouraging extreme positions. Voters in safe districts often feel their vote doesn't matter, depressing turnout.

Distorted Representation

Gerrymandering can allow a party to win a majority of seats with a minority of votes. In 2012, Democratic House candidates nationwide received about 1.4 million more votes than Republican candidates, yet Republicans won a 33-seat majority in the chamber. This "efficiency gap"—the difference between wasted votes for each party—is a common measure of partisan gerrymandering.

Racial Discrimination

Though the Voting Rights Act of 1965 sought to protect minority voters, gerrymandering can still dilute their influence. "Racial gerrymandering" occurs when districts are drawn with the intent to harm minority groups, often by packing them together or cracking them across white-majority districts. The Supreme Court has ruled that race cannot be the predominant factor in drawing district lines, but proving intent remains difficult.

Polarization and Gridlock

Safe districts tend to elect ideologically extreme candidates who can ignore moderate voters. This leads to a Congress where members have little incentive to compromise, contributing to legislative gridlock. As a result, public trust in government erodes, and voters feel disconnected from the political process.

Who Draws the Lines? The Redistricting Process

In most U.S. states, state legislatures draw congressional and legislative district lines after each decennial census. This inherently creates a conflict of interest: the very politicians who benefit from gerrymandering control the redistricting pen. A handful of states—such as California, Arizona, Michigan, and Colorado—have shifted power to independent or bipartisan commissions. Studies show that commission-drawn maps are significantly less gerrymandered than legislatively drawn ones.

The process typically follows these steps:

  1. Census data released: The U.S. Census Bureau provides detailed population counts at the block level.
  2. Apportionment: Each state learns how many House seats it gets. Some gain, some lose.
  3. State redistricting: The legislature or commission drafts a map, often using sophisticated software.
  4. Legal review: Maps can be challenged in court for violating the Constitution or the Voting Rights Act.
  5. Final adoption: The map is approved and used for the next decade.

Efforts to Combat Gerrymandering

Independent Redistricting Commissions

Reformers advocate for taking redistricting out of politicians' hands. As of 2026, about 14 states use commissions with varying degrees of independence. The most effective models, like Arizona's Independent Redistricting Commission, require bipartisan cooperation and public hearings. These commissions have produced maps that better reflect the state's partisan balance.

Federal courts have been inconsistent in ruling on partisan gerrymandering. In Vieth v. Jubelirer (2004), the Supreme Court declared that partisan gerrymandering claims were "nonjusticiable"—meaning courts couldn't hear them—because there was no manageable standard. However, in Gill v. Whitford (2018), the Court sidestepped the issue by ruling that plaintiffs lacked standing. Later, Rucho v. Common Cause (2019) definitively ruled that federal courts cannot hear partisan gerrymandering cases, leaving the matter to state courts and legislatures.

State courts have stepped into the breach. In states like Pennsylvania, North Carolina, and Ohio, state supreme courts have struck down gerrymandered maps under state constitutions' free elections clauses. These decisions have created a patchwork of protections, depending on the state's judicial makeup.

Ballot Initiatives and Voter Action

In states that allow citizen initiatives, voters have directly enacted reform. Michigan's 2018 Proposal 2 created an independent commission; Ohio voters passed anti-gerrymandering measures in 2015 and 2018; Colorado's Amendment Y (2018) did the same. However, these reforms face ongoing legal challenges and pushback from legislators who want to reclaim control.

Mathematical and Technological Solutions

Researchers have developed algorithms that draw "neutral" maps—districts that are compact, respect communities of interest, and avoid partisan bias. Tools like the "efficiency gap" (developed by political scientist Eric McGhee) and "mean-median difference" quantify how much a map favors one party. While courts have not adopted these metrics as legal standards, they help advocacy groups expose egregious maps.

One promising approach is the "fair voting map" concept, which uses math to minimize partisan advantage while maintaining traditional redistricting criteria like contiguity and equal population. For example, the Princeton Gerrymandering Project evaluates maps on multiple fairness dimensions and releases public grades.

Gerrymandering Beyond the United States

The practice is not unique to America. In the United Kingdom, a similar tactic called "boundary manipulation" has historically favored the Conservative Party. In Malaysia, electoral boundaries have been drawn to favor the ruling coalition, especially in rural districts. Canada, Australia, and New Zealand use independent boundary commissions that largely depoliticize the process. The most extreme cases occur in authoritarian regimes, where the map is used to suppress opposition entirely.

International observers often note that the U.S. is an outlier in allowing partisan control of redistricting. Most democracies entrust boundary drawing to neutral bodies—a reform that many American activists seek to emulate.

Real-World Examples of Gerrymandering

North Carolina's Congressional Maps (2010s)

In 2016, a federal court struck down North Carolina's congressional map, ruling that it was an unconstitutional partisan gerrymander. The map, drawn by Republicans, had created 10 Republican-leaning districts and 3 Democratic-leaning ones, even though the state was roughly evenly divided. The court noted that the map was designed to elect as many Republicans as possible—a statement that the map's architect, Representative David Lewis, openly admitted.

Maryland's 3rd District

Often called one of the most gerrymandered districts in the country, Maryland's 3rd District wound through multiple counties, connecting Democratic strongholds while splitting Republican areas. After the 2010 census, Democrats drew a map that gave them seven out of eight House seats in a state where they won about 60% of the vote. A federal lawsuit failed to overturn it, but the map's bizarre shape—sometimes described as "a praying mantis"—became a poster child for reform.

Ohio's State Legislative Maps

In the 2020s, Ohio became a battleground over gerrymandering. The state's redistricting commission, composed mainly of elected officials, repeatedly produced maps that gave Republicans a supermajority of seats despite close statewide elections. The Ohio Supreme Court struck down these maps as "undemocratic" only to have Republican commissioners delay and produce new maps that the court again rejected. The saga illustrates how determined lawmakers can resist judicial intervention.

The Future of Gerrymandering

Two major trends are shaping the future: technology and legal evolution. Artificial intelligence and advanced GIS software (like the open-source project "redistrict") allow anyone to draw maps with precision. This makes gerrymandering easier but also makes detection easier—journalists and researchers can now run simulations to see if a map is an outlier compared to thousands of randomly drawn alternatives.

At the same time, state-level legal victories are creating a new body of precedent. The U.S. Supreme Court's decision in Rucho v. Common Cause closed the federal courthouse door, but state courts are increasingly willing to enforce stronger protections. The "State Redistricting, Elections, and Democracy Reform" movement has pushed for constitutional amendments in several states.

Another wildcard is the 2030 census and the ensuing redistricting cycle. Rapid demographic changes—the growth of diverse suburban communities, the rising proportion of non-voters, and the increasing accuracy of voter registration files—will give mapmakers ever more data. Reformers argue that only binding, transparent, and independent redistricting processes can prevent the next wave of extreme gerrymandering.

For voters, the best defense is awareness. Understanding how districts are drawn—and who draws them—is the first step toward demanding accountability. Groups like the Common Cause and Brennan Center for Justice provide detailed reports on gerrymandering around the country. The Princeton Gerrymandering Project offers an interactive tool to evaluate any state's maps. And the ACLU continues to fight gerrymandering through litigation.

In a healthy democracy, voters choose their representatives—not the other way around. Gerrymandering inverts that relationship, letting politicians pick their electorate. Until fundamental reforms are enacted nationwide, the fight for fair maps will remain one of the most important—and underreported—battles in American politics.