Every ten years, after the U.S. Census counts the population, state legislatures redraw the boundaries of congressional and state legislative districts. The process is supposed to ensure equal representation as populations shift. Instead, in most states, it has become a tool for entrenching political power regardless of how people actually vote.
Gerrymandering — the practice of drawing district lines to favor one party over another — is not a glitch in American democracy. It is a feature that both parties have used when they control the mapmaking process. The result: millions of voters live in districts where the outcome is predetermined, where their vote functionally does not matter, and where accountability to constituents has been replaced by accountability to the party that drew the lines.
The stakes are measurable. In the 2022 midterm elections, Republicans won 222 House seats with 50.6 percent of the national popular vote. Democrats won 213 seats with 47.7 percent. That margin — nine seats — was smaller than the number of seats political scientists attribute to gerrymandering in just four states: North Carolina, Ohio, Texas, and Florida. The maps, not the voters, decided control of Congress.
This is not a story about one party rigging elections while the other plays fair. Democrats gerrymandered Illinois and Maryland. Republicans gerrymandered far more states, and did so more aggressively, after winning control of state legislatures in the 2010 midterms. The asymmetry matters because it shapes who holds power in Washington and in state capitals — and because the party that benefits from the current system has no incentive to change it.
What is gerrymandering?
Gerrymandering is the deliberate manipulation of electoral district boundaries to advantage one political party or group over another. The term dates to 1812, when Massachusetts Governor Elbridge Gerry signed a redistricting plan that created a district so contorted it resembled a salamander. A political cartoonist combined Gerry's name with "salamander," and the word stuck.
The practice is older than the term. Patrick Henry tried to gerrymander James Madison out of Congress in 1788. What has changed is the scale and precision. Modern gerrymandering uses voter data, precinct-level election results, demographic information, and mapping software to draw districts with surgical accuracy. Mapmakers can predict, down to a few percentage points, how a district will vote before a single ballot is cast.
Gerrymandering is legal. The Supreme Court ruled in Rucho v. Common Cause (2019) that federal courts cannot hear challenges to partisan gerrymandering because there is no clear constitutional standard for when a map becomes too partisan. Chief Justice John Roberts, writing for the 5-4 majority, acknowledged that "excessive partisanship in districting leads to results that reasonably seem unjust," but concluded that the question was political, not judicial. The decision left redistricting reform to state legislatures — the same bodies that benefit from gerrymandered maps.
State courts can still strike down gerrymanders under state constitutions, and some have. But in most states, the party in power draws the maps, and the maps stay in place for a decade. The U.S. Congress has the constitutional authority to regulate congressional elections, but it has not passed redistricting reform legislation in decades.
How does gerrymandering work?
Gerrymandering works by concentrating the opposing party's voters into a small number of districts where they win by large margins, and spreading the rest across many districts where they lose by smaller margins. The result: one party wins more seats with fewer votes.
The process begins with data. Mapmakers use voter files that include party registration, voting history, race, age, and address. They layer in precinct-level results from recent elections. Mapping software allows them to test thousands of configurations, adjusting boundaries block by block until they find a map that maximizes their party's seat advantage.
Geography helps. Democratic voters are more concentrated in urban areas, which makes them easier to pack into a few districts. Republican voters are more evenly distributed across suburban and rural areas, which makes it easier to draw maps that give Republicans a structural advantage even in states where the statewide vote is close. But geography is not destiny — it is a tool that skilled mapmakers exploit.
The Brennan Center for Justice analyzed the 2021-2022 redistricting cycle and found that partisan gerrymandering gave Republicans a net advantage of 16 to 17 seats in the U.S. House of Representatives. That advantage came from aggressive gerrymanders in states like Texas, Florida, and Georgia, where Republicans controlled the redistricting process, and from Democratic gerrymanders in states like Illinois and New York that were less aggressive or, in New York's case, struck down by state courts.
Gerrymandering does not require a conspiracy. It requires only that one party control the redistricting process and use that control to maximize its advantage. The incentive structure is clear: the party that draws the maps can lock in power for a decade, insulating itself from electoral swings and reducing the need to appeal to swing voters. The cost is borne by voters whose preferences are diluted or ignored.
The two types: packing and cracking
Gerrymandering relies on two techniques: packing and cracking. Both manipulate the geographic distribution of voters to produce a predetermined outcome.
Packing concentrates the opposing party's voters into as few districts as possible. Those districts become safe seats for the opposition, often with 70 or 80 percent of the vote going to one party. The goal is not to eliminate the opposition entirely — that would be impossible and would invite legal challenges — but to contain it. By packing opposition voters into a small number of districts, mapmakers waste those votes. Winning a district with 80 percent of the vote is no more valuable than winning with 51 percent, but it removes tens of thousands of voters from competitive districts where they might have made a difference.
Example: Illinois's 4th Congressional District, drawn by Democrats, connects two predominantly Latino neighborhoods on Chicago's North and South sides with a thin strip of land along Interstate 294. The district is more than 70 percent Hispanic and reliably Democratic. The shape is not accidental. By packing Democratic voters into the 4th District, mapmakers freed up surrounding districts to be more competitive or to lean Republican, depending on the configuration.
Cracking splits the opposing party's voters across multiple districts, diluting their voting power so they cannot win a majority in any of them. Cracking is harder to see on a map because the districts may look relatively compact. The giveaway is in the election results: districts that should be competitive based on statewide voting patterns instead lean heavily toward one party.
Example: Wisconsin's state legislative maps, drawn by Republicans after the 2010 census, cracked Democratic voters in Madison and Milwaukee across multiple districts. In the 2018 election, Democrats won 53 percent of the statewide vote for the state Assembly but won only 36 of 99 seats — a 37 percent seat share. The maps were so effective that even in a Democratic wave year, Republicans maintained a supermajority. Wisconsin's Supreme Court struck down those maps in 2023, but they had been in place for more than a decade.
Packing and cracking often work together. A mapmaker might pack opposition voters into one or two districts, then crack the remainder across several districts where they are outnumbered. The result is a map where one party wins a large majority of seats even when the statewide vote is close to 50-50.
Which states are most gerrymandered?
Gerrymandering is not evenly distributed. Some states have independent redistricting commissions or court-imposed maps. Others have maps drawn by state legislatures with no meaningful oversight. The most gerrymandered states share a common feature: one party controls the redistricting process and uses that control aggressively.
North Carolina. Republicans control the state legislature and have drawn some of the most aggressive gerrymanders in the country. After the 2020 census, the legislature passed a congressional map that gave Republicans a 10-4 advantage in a state where the statewide vote is typically 51-49 or 50-50. In the 2022 midterms, Republicans won 10 of 14 seats with 50.7 percent of the vote. The state Supreme Court struck down the map in 2022, but a newly elected Republican majority on the court reversed that decision in 2023, allowing the gerrymandered map to stand.
Ohio. Republicans drew a congressional map that gives them a 13-2 advantage in a state that voted 53-45 for Donald Trump in 2020. Ohio voters passed a constitutional amendment in 2015 requiring bipartisan support for redistricting, but the legislature ignored it. The state Supreme Court struck down multiple versions of the map, and the legislature passed new maps that were functionally identical. Eventually, the court allowed the maps to stand for the 2022 election because there was no time to draw new ones. The gerrymandered maps remain in place.
Texas. Republicans control redistricting and have used that power to entrench their majority even as the state's population becomes more diverse and Democratic-leaning. The 2021 congressional map gave Republicans a 25-13 advantage despite the statewide vote being closer to 52-48. The map also diluted the voting power of Latino voters, who accounted for half of Texas's population growth in the 2010s but gained no new majority-Latino districts. Federal courts have found that Texas's maps violate the Voting Rights Act, but the maps remain in effect while litigation continues.
Florida. Republicans control the legislature, and Governor Ron DeSantis personally intervened in the 2022 redistricting process to demand a more aggressive gerrymander. The resulting map eliminated two districts where Black voters had elected their preferred candidates and gave Republicans a 20-8 advantage in a state where the statewide vote is typically 51-49. A state court ruled that the map violated Florida's constitution, but the decision was stayed pending appeal, and the map was used in the 2022 election. Republicans have since pushed the Florida gerrymander even further, passing new lines that would expand their advantage to 24-4.
Georgia. Republicans drew a congressional map that maintained their 9-5 advantage despite population growth in Democratic-leaning Atlanta suburbs. The map cracked Gwinnett County, a diverse suburban county east of Atlanta, across multiple districts to prevent the formation of a new Democratic-leaning seat. A federal court found that the map likely violated the Voting Rights Act by diluting Black voting power, but the map remains in place.
Wisconsin. Republicans drew state legislative maps after the 2010 census that gave them a durable majority even when Democrats won the statewide vote. The maps were so effective that in 2012, Democrats won 51 percent of the statewide vote for the state Assembly but won only 39 of 99 seats. The Wisconsin Supreme Court struck down the maps in 2023 after the court's ideological balance shifted, but the maps had been in place for 13 years.
Democrats have also gerrymandered, though less aggressively and in fewer states. Illinois Democrats drew a congressional map that gave them a 14-3 advantage in a state that voted 57-41 for Joe Biden in 2020. Maryland Democrats drew a map that gave them a 7-1 advantage in a state that voted 65-33 for Biden. Both maps were challenged in court, and both survived.
The asymmetry is not accidental. Republicans controlled redistricting in more states after the 2020 census because they won control of more state legislatures in the 2010 midterms. That advantage compounded over the decade, as gerrymandered maps made it harder for Democrats to win back those legislatures. The result is a structural advantage that persists regardless of how the national political environment shifts.
How gerrymandering affects elections
Gerrymandering does not determine every election outcome, but it shapes the range of possible outcomes. In a gerrymandered state, one party can win a comfortable majority of seats even when it loses the statewide popular vote. That distortion has consequences for representation, accountability, and policy.
Reduced competition. Gerrymandering creates safe seats where the general election is not competitive. The real contest is the primary, where the electorate is smaller, more ideologically extreme, and more responsive to party activists than to the median voter. The result is a legislature that is more polarized than the electorate it represents. According to the Brennan Center, the number of competitive U.S. House seats — defined as seats where the margin of victory is less than 10 percentage points — has declined from more than 100 in the 1990s to fewer than 40 in 2022. Gerrymandering is not the only cause, but it is a significant one.
Minority rule. Gerrymandering allows a party to win a majority of seats with a minority of votes. In Wisconsin's 2018 state Assembly election, Democrats won 53 percent of the statewide vote but only 36 percent of the seats. In North Carolina's 2022 congressional election, Republicans won 50.7 percent of the vote but 71 percent of the seats. The gap between vote share and seat share is a direct measure of how much the maps, rather than the voters, are determining outcomes.
Weakened accountability. In a gerrymandered district, the incumbent does not need to appeal to swing voters or respond to shifts in public opinion. The district is designed to be safe. That insulation reduces the incentive to compromise, to build coalitions, or to represent the full range of views within the district. It also makes it harder for voters to hold their representatives accountable. If the district is drawn to be 60-40 or 65-35, the incumbent can ignore the 40 or 35 percent who voted for the other party without electoral consequence.
Policy distortion. Gerrymandering affects not just who wins elections, but what policies those winners pursue. In states where one party has a gerrymandered majority, that party can pass legislation that does not reflect the preferences of the median voter. Wisconsin's Republican-controlled legislature, elected from gerrymandered maps, blocked Medicaid expansion even though polling showed that a majority of Wisconsin voters supported it. North Carolina's Republican-controlled legislature passed strict voting restrictions and bathroom bills targeting transgender people, policies that were unpopular statewide but played well in gerrymandered districts.
Gerrymandering also affects national policy. Control of the U.S. House of Representatives has been decided by narrow margins in recent elections. In 2022, Republicans won a nine-seat majority. Political scientists estimate that gerrymandering gave Republicans a 16-17 seat advantage. Without that advantage, Democrats would likely have held the House, and the legislative agenda for the next two years would have been entirely different.
What is being done to stop gerrymandering?
Efforts to stop gerrymandering fall into three categories: independent redistricting commissions, state constitutional amendments, and federal legislation. Progress has been uneven, and the party that benefits from the current system has little incentive to change it.
Independent redistricting commissions. Eleven states use independent or bipartisan commissions to draw congressional or state legislative maps. The commissions vary in structure, but the goal is the same: remove the redistricting process from the direct control of the legislature. States with independent commissions include Arizona, California, Colorado, Idaho, Michigan, Montana, New Jersey, Washington, and Alaska. Voters in these states passed ballot initiatives or constitutional amendments to create the commissions, often over the objection of state legislatures.
The results are mixed. California's independent commission, created by a 2008 ballot initiative, has produced maps that are more competitive than the legislature-drawn maps they replaced. Michigan's commission, created by a 2018 ballot initiative, drew maps that were significantly less gerrymandered than the Republican-drawn maps from the previous decade. But commissions are not a panacea. Arizona's commission has been criticized for producing maps that still favor one party, and the commission's decisions have been challenged in court multiple times.
State constitutional amendments. Several states have amended their constitutions to impose redistricting criteria such as compactness, respect for communities of interest, and limits on partisan advantage. Ohio voters passed a constitutional amendment in 2015 requiring bipartisan support for redistricting, but the legislature ignored it and passed gerrymandered maps anyway. Florida voters passed a constitutional amendment in 2010 prohibiting maps drawn to favor a political party, but the 2022 maps, drawn at Governor DeSantis's direction, violated that amendment and remain in place while litigation continues.
Constitutional amendments are only as strong as the enforcement mechanism. If state courts are unwilling or unable to strike down maps that violate the constitution, the amendments are symbolic.
Federal legislation. The Freedom to Vote Act and the John Lewis Voting Rights Advancement Act, both introduced in Congress in 2021, would have established federal standards for redistricting, including requirements for independent commissions and limits on partisan gerrymandering. Both bills passed the House but were blocked in the Senate by the filibuster. Senate Democrats attempted to change the filibuster rules to pass the bills with a simple majority, but the effort failed when two Democratic senators, Joe Manchin and Kyrsten Sinema, refused to support it.
Federal redistricting reform is unlikely in the near term. Republicans control the House and oppose federal redistricting standards, arguing that redistricting is a state matter. Democrats support reform, but they do not have the votes to pass it. The result is a stalemate that benefits the party in power.
Litigation. Voting rights groups have challenged gerrymandered maps in state and federal courts, with mixed results. The Supreme Court's decision in Rucho v. Common Cause closed the door to federal challenges based on partisan gerrymandering, but state courts can still strike down maps under state constitutions. In 2022 and 2023, state courts in North Carolina, Ohio, New York, and Pennsylvania struck down gerrymandered maps, forcing legislatures to redraw them. But in North Carolina and Ohio, the legislatures passed new maps that were functionally identical to the old ones, and the courts eventually allowed them to stand. In Virginia, a state supreme court ruling erased four Democratic seats before a single vote was cast, illustrating how judicial decisions can reshape the political map as decisively as any legislature.
Litigation is slow, expensive, and uncertain. By the time a court strikes down a map, it may have been in place for several election cycles. And even when courts order new maps, there is no guarantee that the new maps will be significantly less gerrymandered.
Why it matters now. The next round of redistricting will occur after the 2030 census. The party that controls state legislatures in 2031 will draw the maps that determine representation for the following decade. That makes the 2028 and 2030 state legislative elections pivotal. Voting rights groups and political parties are already preparing for those elections, knowing that control of redistricting is at stake.
Gerrymandering is not a technical problem. It is a power problem. The party that controls the mapmaking process has the power to entrench itself for a decade, insulating itself from electoral accountability and reducing the need to appeal to swing voters. The solution is not better software or clearer criteria. The solution is removing the redistricting process from the control of the politicians whose careers depend on the outcome. That requires political will, and political will requires voters to demand it.
In states where voters have had the opportunity to pass redistricting reform through ballot initiatives, they have done so by wide margins, often with bipartisan support. The public understands that the current system is rigged. What remains to be seen is whether the politicians who benefit from that system will allow it to change — or whether voters will force the issue by electing legislators who will.
