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Explainer

Gerrymandering Explained

The practice has been a thorn in the side of democracy for centuries, and with the new round of redistricting it’s a bigger threat than ever.

Last Updated: August 12, 2021
Published: August 10, 2021
redistricting map
Duane Howell/The Denver Post via Getty Images

After the Census Bureau releases detailed popu­la­tion and demo­graphic data from the 2020 census on August 12, states and local govern­ments begin the once-a-decade process of draw­ing new voting district bound­ar­ies known as redis­trict­ing. And gerry­man­der­ing — when those bound­ar­ies are drawn with the inten­tion of influ­en­cing who gets elec­ted — is bound to follow.

The current redis­trict­ing cycle will be the first since the Supreme Court’s 2019 ruling that gerry­man­der­ing for party advant­age cannot be chal­lenged in federal court, which has set the stage for perhaps the most omin­ous round of map draw­ing in the coun­try’s history.

Here are six things to know about partisan gerry­man­der­ing and how it impacts our demo­cracy.

Gerry­man­der­ing is deeply undemo­cratic.

Every 10 years, states redraw their legis­lat­ive and congres­sional district lines follow­ing the census. Because communit­ies change, redis­trict­ing is crit­ical to our demo­cracy: maps must be redrawn to ensure that districts are equally popu­lated, comply with laws such as the Voting Rights Act, and are other­wise repres­ent­at­ive of a state’s popu­la­tion. Done right, redis­trict­ing is a chance to create maps that, in the words of John Adams, are an “exact portrait, a mini­ature” of the people as a whole.

But some­times the process is used to draw maps that put a thumb on the scale to manu­fac­ture elec­tion outcomes that are detached from the pref­er­ences of voters. Rather than voters choos­ing their repres­ent­at­ives, gerry­man­der­ing empowers politi­cians to choose their voters. This tends to occur espe­cially when linedraw­ing is left to legis­latures and one polit­ical party controls the process, as has become increas­ingly common. When that happens, partisan concerns almost invari­ably take preced­ence over all else. That produces maps where elect­oral results are virtu­ally guar­an­teed even in years where the party draw­ing maps has a bad year.

There are multiple ways to gerry­mander.

While legis­lat­ive and congres­sional district shapes may look wildly differ­ent from state to state, most attempts to gerry­mander can best be under­stood through the lens of two basic tech­niques: crack­ing and pack­ing.

Crack­ing splits groups of people with similar char­ac­ter­ist­ics, such as voters of the same party affil­i­ation, across multiple districts. With their voting strength divided, these groups struggle to elect their preferred candid­ates in any of the districts.

gerrymandering cracking

Pack­ing is the oppos­ite of crack­ing: map draw­ers cram certain groups of voters into as few districts as possible. In these few districts, the “packed” groups are likely to elect their preferred candid­ates, but the groups’ voting strength is weakened every­where else.

gerrymandering packing

Some or all of these tech­niques may be deployed by map draw­ers in order to build a partisan advant­age into the bound­ar­ies of districts. A key note, however: while some­times gerry­man­der­ing results in oddly shaped districts, that isn’t always the case. Crack­ing and pack­ing can often result in regu­larly shaped districts that look appeal­ing to the eye but nonethe­less skew heav­ily in favor of one party.

Gerry­man­der­ing has a real impact on the balance of power in Congress and many state legis­latures.

In 2010, Repub­lic­ans — in an effort to control the draw­ing of congres­sional maps — forged a campaign to win major­it­ies in as many state legis­latures as possible. It was wildly success­ful, giving them control over the draw­ing of 213 congres­sional districts. The redraw­ing of maps that followed produced some of the most extreme gerry­manders in history. In battle­ground Pennsylvania, for example, the congres­sional map gave Repub­lic­ans a virtual lock on 13 of the state’s 18 congres­sional districts, even in elec­tions where Demo­crats won the major­ity of the statewide congres­sional vote.

Nation­ally, extreme partisan bias in congres­sional maps gave Repub­lic­ans a net 16 to 17 seat advant­age for most of last decade. Michigan, North Caro­lina, and Pennsylvania alone — the three states with the worst gerry­manders in the last redis­trict­ing cycle — accoun­ted for 7 to 10 extra Repub­lican seats in the House.

On the state level, gerry­man­der­ing has also led to signi­fic­ant partisan bias in maps. For example, in 2018, Demo­crats in Wiscon­sin won every statewide office and a major­ity of the statewide vote, but thanks to gerry­man­der­ing, won only 36 of the 99 seats in the state assembly.

Though Repub­lic­ans were the primary bene­fi­ciar­ies of gerry­man­der­ing last decade, Demo­crats have also used redis­trict­ing for partisan ends: in Mary­land, for instance, Demo­crats used control over map-draw­ing to elim­in­ate one of the state’s Repub­lican congres­sional districts.

Regard­less of which party is respons­ible for gerry­man­der­ing, it is ulti­mately the public who loses out. Rigged maps make elec­tions less compet­it­ive, in turn making even more Amer­ic­ans feel like their votes don’t matter.

Gerry­man­der­ing affects all Amer­ic­ans, but its most signi­fic­ant costs are borne by communit­ies of color.

Resid­en­tial segreg­a­tion and racially polar­ized voting patterns, espe­cially in south­ern states, mean that target­ing communit­ies of color can be an effect­ive tool for creat­ing advant­ages for the party that controls redis­trict­ing. This is true regard­less of whether it is Demo­crats or Repub­lic­ans draw­ing the maps.

The Supreme Court’s 2019 decision in Rucho v. Common Cause green­light­ing partisan gerry­man­der­ing has made things worse. The Voting Rights Act and the Consti­tu­tion prohibit racial discrim­in­a­tion in redis­trict­ing. But because there often is correl­a­tion between party pref­er­ence and race, Rucho opens the door for Repub­lican-controlled states to defend racially discrim­in­at­ory maps on grounds that they were permiss­ibly discrim­in­at­ing against Demo­crats rather than imper­miss­ibly discrim­in­at­ing against Black, Latino, or Asian voters.

Target­ing the polit­ical power of communit­ies of color is also often a key element of partisan gerry­man­der­ing. This is espe­cially the case in the South, where white Demo­crats are a compar­at­ively small part of the elect­or­ate and often live, prob­lem­at­ic­ally from the stand­point of a gerry­man­derer, very close to white Repub­lic­ans. Even with slicing and dicing, discrim­in­at­ing against white Demo­crats only moves the polit­ical dial so much. Because of resid­en­tial segreg­a­tion, it is much easier for map draw­ers to pack or crack communit­ies of color to achieve maximum polit­ical advant­age.

Gerry­man­der­ing is getting worse.

Gerry­man­der­ing is a polit­ical tactic nearly as old as the United States. In design­ing Virgini­a’s very first congres­sional map, Patrick Henry attemp­ted to draw district bound­ar­ies that would block his rival, James Madison, from winning a seat. But gerry­man­der­ing has also changed dramat­ic­ally since the found­ing: today, intric­ate computer algorithms and soph­ist­ic­ated data about voters allow map draw­ers to game redis­trict­ing on a massive scale with surgical preci­sion. Where gerry­man­der­ers once had to pick from a few maps drawn by hand, they now can create and pick from thou­sands of computer-gener­ated maps.

Gerry­man­der­ing also looks likely to get worse because the legal frame­work govern­ing redis­trict­ing has not kept up with demo­graphic changes. Before, most people of color in the coun­try’s metro areas lived in highly segreg­ated cities. Today, however, a major­ity of Black, Latino, and Asian Amer­ic­ans live in diverse suburbs. This change has given rise to power­ful new multiracial voting coali­tions outside cities such as Atlanta, Dallas, and Hous­ton that have won or come close to winning power. Yet the Supreme Court has not gran­ted these multiracial coali­tion districts the same legal protec­tions as major­ity-minor­ity districts, making them a key target for dismant­ling by partisan map draw­ers.

Federal reform can help counter gerry­man­der­ing — but Congress needs to act soon.

The For the People Act, a land­mark piece of federal demo­cracy reform legis­la­tion that has already passed the House, repres­ents a major step toward curb­ing polit­ical games­man­ship in map draw­ing. The bill would enhance trans­par­ency, strengthen protec­tions for communit­ies of color, and ban partisan gerry­man­der­ing in congres­sional redis­trict­ing. It would also improve voters’ abil­ity to chal­lenge gerry­mandered maps in court.

With redis­trict­ing now begin­ning in many states, the need for Congress to pass reform legis­la­tion is more urgent than ever. Unless that happens, we risk another decade of racially and polit­ic­ally discrim­in­at­ory line-draw­ing. But time is running short. The Census Bureau released data to the states for redis­trict­ing on August 12. If new laws are to have the maximum impact, Congress needs to act quickly. Fair repres­ent­a­tion depends on it.