Gerrymandering: How Politicians Choose Their Voters Before Voters Choose Them

You live somewhere. That somewhere is inside a congressional district. That district determines which House member represents you, which state legislative candidates appear on your ballot, and how much your vote actually matters.

Every 10 years, after the census, those district lines get redrawn. In most states, the politicians who won the last election get to draw the maps for the next one. That is gerrymandering: the practice of drawing district boundaries to predetermine election outcomes.

What Gerrymandering Actually Is

Gerrymandering is manipulating the boundaries of electoral districts to give one party (or group) an artificial advantage. The word comes from Elbridge Gerry, the governor of Massachusetts who signed a redistricting bill in 1812 that created a district so contorted it looked like a salamander. A newspaper cartoonist combined Gerry's name with "salamander" and called it a "Gerry-mander." The name stuck.

The core idea has not changed in 200 years. If you control how the lines are drawn, you control who wins.

How It Works: Packing and Cracking

Gerrymandering relies on two basic techniques. Both exploit the same principle: it does not matter how many total votes a party gets statewide. What matters is how those votes are distributed across districts.

Packing means concentrating the opposing party's voters into as few districts as possible. You let them win those districts by huge margins (80-90%) so their votes are "wasted" on blowout victories. Every vote above 50%+1 in a district does nothing to help win additional seats.

Cracking means splitting the opposing party's voters across multiple districts so they fall short of a majority in each one. A city that would naturally form one or two strong districts for one party gets carved into five or six pieces, each attached to surrounding rural areas where the other party dominates.

A Simple Example

Imagine a state with 50 voters: 30 blue, 20 red. The state gets 5 districts of 10 voters each. A proportional outcome would be 3 blue seats and 2 red seats.

If blue draws the map: Pack red voters into 1 district (10 red, 0 blue). Spread blue voters across the other 4 (roughly 7-8 blue, 2-3 red each). Result: Blue wins 4 seats, red wins 1. Blue has 60% of voters but 80% of seats.

If red draws the map: Pack blue voters into 2 districts (10 blue each, guaranteed blue blowouts). Spread the remaining 10 blue and all 20 red across the other 3 districts (roughly 3 blue, 7 red each). Result: Red wins 3 seats, blue wins 2. Red has only 40% of voters but 60% of seats.

This is a simplified version, but the math scales. With modern data and mapping software, map-drawers can do this with surgical precision across hundreds of districts simultaneously.

Why It Is So Effective Now

Gerrymandering is not new, but it has become dramatically more powerful because of three things:

1. Voter data. Political parties now have access to detailed data on every registered voter: party registration, voting history, demographics, consumer behavior, even magazine subscriptions. They know with high confidence how nearly every household will vote.

2. Mapping software. Computers can generate and evaluate thousands of possible maps in hours. Software like Dave's Redistricting App (which is publicly available) or proprietary tools used by party operatives can optimize maps for partisan advantage at a level of precision that was impossible when lines were drawn by hand.

3. Geographic sorting. Americans have increasingly sorted themselves by politics. Democratic voters concentrate in cities. Republican voters dominate rural areas. This natural clustering makes cracking and packing easier because the raw material (concentrated opposing voters) is already there.

How Redistricting Works

The Census, required by the Constitution every 10 years, counts every person in the country. After the count, the 435 House seats are apportioned among the states based on population. States that grew faster gain seats. States that grew slower lose them.

Then each state redraws its district maps so every district has roughly equal population (the "one person, one vote" principle from Reynolds v. Sims, 1964).

Who draws the maps varies by state:

State legislatures draw the maps in most states. The party that controls the legislature controls the process. This is where most gerrymandering happens.
Independent commissions draw maps in some states (Arizona, California, Colorado, Michigan, Virginia, and others). These commissions are designed to remove partisan control from the process.
Politician commissions exist in a few states, where elected officials serve on the redistricting body but with some constraints.
Courts sometimes step in when maps are challenged, either drawing their own maps or ordering the legislature to try again.

The most recent redistricting happened after the 2020 Census. The maps drawn in 2021-2022 are the ones in use today and will be used through the 2030 elections.

Partisan Gerrymandering vs. Racial Gerrymandering

Courts treat these two types of gerrymandering very differently.

Partisan Gerrymandering

In Rucho v. Common Cause (2019), the Supreme Court ruled 5-4 that partisan gerrymandering is a "political question" that federal courts cannot resolve. The majority opinion, written by Chief Justice Roberts, acknowledged that "excessive partisanship in districting leads to results that reasonably seem unjust" but concluded there is no manageable standard for courts to decide when partisan gerrymandering crosses a constitutional line.

This means: federal courts will not stop partisan gerrymandering, no matter how extreme. A state legislature can openly design maps to maximize its party's seats, and the federal judiciary will not intervene.

The ruling did not say gerrymandering is good or constitutional. It said federal courts are the wrong institution to police it. Roberts pointed to state courts, state constitutions, independent commissions, and Congress as the proper venues for reform.

Racial Gerrymandering

The Voting Rights Act of 1965 and the 14th and 15th Amendments prohibit drawing districts to dilute the voting power of racial minorities. Federal courts can and do strike down maps on racial gerrymandering grounds.

But the line between racial and partisan gerrymandering is blurry. Because race and party affiliation are correlated (Black voters, for example, overwhelmingly vote Democratic), a map designed for partisan advantage can look identical to one designed for racial advantage. Legislatures often argue their maps were drawn for partisan reasons, not racial ones, because partisan gerrymandering is legal and racial gerrymandering is not.

In Alexander v. South Carolina State Conference of the NAACP (2024), the Supreme Court made it harder to prove racial gerrymandering by ruling that when race and party are highly correlated, challengers must provide evidence that race was the "predominant" factor, not just a factor. If the legislature can offer a plausible partisan explanation, that is usually enough.

What Gerrymandered Maps Look Like

The most obviously gerrymandered districts have bizarre shapes: long tentacles reaching into specific neighborhoods, narrow corridors connecting distant communities, boundaries that split cities, counties, and neighborhoods in ways that make no geographic sense.

But shape alone does not prove gerrymandering. Some naturally gerrymandered-looking districts exist because of geographic features (rivers, mountains) or because they are drawn to comply with the Voting Rights Act by creating majority-minority districts. And some of the most effective gerrymanders use relatively normal-looking district shapes.

The better test is outcomes. Signs of a gerrymandered map include:

Lopsided margins. One party wins several districts by narrow margins (52-55%) while the other party wins fewer districts by blowout margins (75-90%). This is the signature of packing and cracking.
Seats vs. votes mismatch. A party wins 55% of the statewide vote but gets 70% of the seats.
Uncompetitive elections. Very few districts where the outcome is genuinely uncertain. In a gerrymandered map, most races are decided by the map, not the voters.
Statistical outliers. Compared to thousands of computer-generated maps that follow neutral criteria (equal population, contiguity, compactness), the enacted map consistently favors one party more than virtually all alternatives. This "ensemble analysis" approach has become a key tool in gerrymandering litigation.

The Efficiency Gap and Other Metrics

Researchers have developed quantitative measures of gerrymandering:

The efficiency gap measures "wasted votes," the votes that do not contribute to electing a representative. Packed voters waste votes on blowout wins. Cracked voters waste votes on losses. A perfectly fair map would waste roughly equal votes for both parties. A gerrymandered map wastes far more of the disadvantaged party's votes.

Mean-median difference compares a party's average vote share across districts to its median vote share. In a symmetric map, these should be similar. A large gap suggests the map is skewed.

Ensemble analysis generates thousands of random maps using neutral criteria and compares them to the enacted map. If the enacted map is a statistical outlier, consistently favoring one party more than 95-99% of randomly generated alternatives, that is strong evidence of gerrymandering. The Princeton Gerrymandering Project and others use this approach.

States That Have Tried to Fix It

Several states have moved redistricting out of the legislature's hands:

California created the Citizens Redistricting Commission in 2008 (Proposition 11). Fourteen citizens, selected through an application and screening process, draw the maps. No current or recent politicians, lobbyists, or political staff can serve. California's districts are now considered among the fairest in the country.

Arizona was an early adopter, creating its Independent Redistricting Commission by ballot initiative in 2000. The legislature challenged it, but the Supreme Court upheld the commission in Arizona State Legislature v. Arizona Independent Redistricting Commission (2015), ruling that "the Legislature" in the Elections Clause includes ballot initiatives.

Michigan voters approved Proposal 2 in 2018, creating a 13-member Independent Citizens Redistricting Commission. The commission drew Michigan's current maps, which were a dramatic departure from the heavily gerrymandered maps the legislature had produced.

Colorado created two independent commissions (one for congressional, one for state legislative) through ballot measures in 2018.

Virginia adopted a bipartisan commission in 2020, though the commission deadlocked along party lines during its first redistricting, and the maps were ultimately drawn by the Virginia Supreme Court.

Other states with some form of commission include Hawaii, Idaho, Iowa, Montana, New Jersey, New York, and Washington, though the structures and levels of independence vary significantly.

Why Congress Has Not Fixed It

Congress has the constitutional authority to set rules for federal elections. It could require independent commissions nationwide, mandate specific redistricting criteria, or ban partisan gerrymandering outright.

The For the People Act (H.R. 1), introduced in the 117th Congress, included provisions requiring independent redistricting commissions for congressional maps. It passed the House in March 2021 but stalled in the Senate. The Freedom to Vote Act (S. 2747) included similar redistricting reforms but never received a Senate floor vote. A combined bill, the Freedom to Vote: John R. Lewis Act (H.R. 5746), passed the House in January 2022 but failed in the Senate, unable to overcome the 60-vote filibuster threshold.

The fundamental problem: the members of Congress who would need to vote for reform are the same people who benefit from the current system. Many of them hold their seats in part because of gerrymandered maps. Asking them to vote for fair maps is asking them to make their own reelection harder.

What Gerrymandering Means for You

Gerrymandering does not just determine which party wins. It changes how government works in several ways:

It makes primaries the real election. In a gerrymandered "safe" district, the general election is a formality. The real competition is the primary, where turnout is low and the most ideologically committed voters have outsized influence. This pulls representatives toward the extremes of their party because they need to survive a primary, not appeal to the general electorate.

It reduces accountability. If your district is drawn so your party always wins by 20+ points, your representative has little incentive to respond to moderate voters or compromise with the other side. The only threat is a primary challenge from someone more extreme.

It contributes to polarization. When most members of Congress come from safe districts where they only need to win a primary, the incentive structure rewards partisan rigidity and punishes compromise. Members who work across the aisle risk being labeled as traitors by their base and getting primaried.

It disconnects seats from votes. In the 2012 House elections, Democratic candidates received 1.4 million more total votes nationwide than Republican candidates. Republicans won 234 seats to Democrats' 201. The maps, drawn after Republicans dominated the 2010 state legislative elections, converted a minority of votes into a majority of seats.

Where Things Stand

After the 2020 Census redistricting cycle, the current maps are considered relatively balanced nationally, though individual states have significant gerrymanders in both directions. Republican-drawn maps in Texas, Florida, Georgia, and Ohio are widely considered to favor Republicans. Democratic-drawn maps in Illinois, Maryland, and New York (after court intervention) favor Democrats.

The next redistricting will happen after the 2030 Census. The state legislative elections in 2028 and 2030 will determine who controls the process in most states. Reform advocates are pushing ballot initiatives for independent commissions in several states ahead of that cycle.

The Supreme Court's position remains that federal courts will not intervene in partisan gerrymandering. State courts, using state constitutional provisions, have become the primary judicial check. The North Carolina Supreme Court struck down maps in 2022, then reversed itself after the court's partisan composition changed in the 2022 elections, illustrating how even judicial review of gerrymandering is shaped by the same partisan dynamics it is supposed to police.

Until either Congress acts, more states adopt independent commissions, or the Supreme Court revisits Rucho, gerrymandering will remain one of the most powerful tools in American politics: invisible to most voters, perfectly legal at the federal level, and built into the structure of representation itself.