How Gerrymandering Works

In 2012, Pennsylvania voters cast more ballots for Democratic congressional candidates than Republican ones. Democrats won the statewide majority. They got five of eighteen seats.

The map had been drawn by the Republican legislature after the 2010 census. It packed Democratic voters into five districts they won by landslides and cracked the rest across thirteen where Republicans held comfortable margins.^[1] Five blowout wins that piled up votes without gaining an extra seat. Thirteen manufactured victories on the other side.

In 2018, the Pennsylvania Supreme Court struck the map down as an unconstitutional gerrymander under the state constitution and ordered new lines drawn with the help of a Stanford redistricting expert.^[1] Under the remedial map, the same electorate sent nine Democrats and nine Republicans to Congress. The only variable was who held the pen.

Whoever holds the pen decides whether the bigger number wins. The people who benefit from district lines are the same people who draw them, and the techniques they use are old enough and simple enough to explain on a napkin.

Cracking splits the opposition's voters across multiple districts so they fall just short of a majority in each one. Maryland's Democratic legislature redrew the 6th Congressional District in 2011 by removing 66,417 registered Republicans and adding 24,460 registered Democrats.^[2] The incumbent, Republican Roscoe Bartlett, had won 61 to 33 the year before. Under the redrawn lines he lost by eleven.

Packing does the opposite. It concentrates the opposition into as few districts as possible so they win those seats by enormous margins and waste votes everywhere else. Pennsylvania's 2012 map used both at once. Five districts drawn to absorb as many Democratic voters as possible, producing lopsided wins that ran up the score for nothing. Thirteen districts carved to include just enough Democrats to dilute their strength without threatening the Republican margin.^[1]

In 2015, Nicholas Stephanopoulos and Eric McGhee published what they called the efficiency gap.^[4] Every vote for a losing candidate is wasted. Every vote for a winner beyond the bare majority needed is wasted. The difference between the two parties' waste totals, divided by total votes, produces a single number measuring how lopsidedly a map converts votes into seats. They argued that an efficiency gap of two seats or more for Congress, or 8 percent for state legislatures, should raise a presumption of an unconstitutional gerrymander.

Wisconsin's assembly map tested the concept. Under a Republican-drawn map from 2010, Democrats won 51 percent of the statewide vote in 2012 and 39 of 99 seats.^[5] The case reached the Supreme Court as Gill v. Whitford. The Court ruled that the plaintiffs lacked standing because they had argued a statewide injury instead of proving they personally lived in a gerrymandered district, and sent the case back without ruling on the merits.^[6] The efficiency gap was never adopted, never rejected.

After the 2020 census, forty-four states had multiple congressional seats. Only eleven gave redistricting to a commission.^[7] The rest left it to their own legislators. Republican state legislatures alone drew 177 congressional districts, 41 percent of the entire House.^[8] In twenty-six states, the maps passed on a party-line vote. In North Carolina in 2018, Republicans won 50 percent of the statewide congressional vote and 77 percent of the seats.^[9]

For fifty years, one federal law kept the worst of it in check. The Voting Rights Act of 1965 required states with a history of racial discrimination to get federal approval before changing any voting rule, including district maps. Between 1965 and 2006, the Department of Justice used that authority to block more than a thousand proposed voting changes before they took effect.^[10]

Three Supreme Court decisions dismantled that constraint. Shelby County v. Holder in 2013 struck down the coverage formula that determined which states needed federal approval.^[11] Preclearance still exists in the statute, but no formula says who's covered, so no one is.^[11] Rucho v. Common Cause in 2019 closed the federal courts to partisan gerrymandering claims entirely, holding that no manageable standard exists to adjudicate them.^[12] Brnovich v. DNC in 2021 raised the bar for challenges under Section 2 of the Voting Rights Act, the last surviving federal avenue for contesting discriminatory maps.^[13]

Then came Louisiana v. Callais.

On April 29, 2026, the Court ruled that Louisiana's second majority-Black congressional district was an unconstitutional racial gerrymander because the Voting Rights Act did not require its creation.^[14] Justice Alito's opinion reached well beyond Louisiana. The Court reworked the forty-year-old framework for racial gerrymandering claims in ways that make future challenges far harder to win. Plaintiffs' proposed alternative maps can no longer use race as a factor and must satisfy all of a state's existing redistricting criteria, including protecting incumbents. Racial-bloc voting must be proved independently of partisan preference. Historical discrimination now carries what the Court called "much less weight," requiring plaintiffs to show present-day intentional discrimination in a country that has spent sixty years learning to discriminate without saying so. Each requirement alone narrows the path for plaintiffs. Together, they close it.

Justice Kagan, dissenting, wrote that the decision "renders Section 2 all but a dead letter."

Redistricting was supposed to happen once a decade, after the census. The Constitution requires a count but says nothing about when states may redraw their maps, and before 2025 only two states had voluntarily redistricted mid-cycle since 1970.^[15]

In 2003, House Majority Leader Tom DeLay decided to test the norm. After Republicans took the Texas legislature, DeLay pushed through a mid-decade re-redistricting to replace the court-drawn maps from 2001. Texas Democrats fled the state to deny a quorum, first to Ardmore, Oklahoma, then to Albuquerque. They came back. The maps passed. The Texas delegation swung from 17 Democrats and 15 Republicans to 21 Republicans and 11 Democrats.^[3] The Supreme Court took the case in LULAC v. Perry and let the mid-decade redistricting stand.

Twenty years later, an entire wave followed. In August 2025, Texas redistricted again at the urging of the White House, which needed to protect the GOP's narrow House majority heading into the midterms. The new map targeted five additional Republican seats. Democrats fled the state a second time, a generation later, to break quorum. California answered in kind. Voters passed Proposition 50, the Election Rigging Response Act, with 64 percent support, suspending the state's independent redistricting commission and substituting a legislature-drawn map projected to add five Democratic seats.^[16]

Between August 2025 and May 2026, at least nine states redrew or attempted to redraw their congressional maps mid-decade.^[18] Callais set off a chain reaction across the South. Eight days after the ruling, Tennessee's legislature convened a special session and passed a map cracking majority-Black Memphis across three districts to eliminate the state's last Democratic House seat.^[17] Analysts project roughly twelve to fourteen seats tilting Republican and nine tilting Democratic, close to a wash in total but a transformation in each redrawn state.^[18]

The once-a-decade cycle was never law. Norms survive when breaking them costs more than keeping them. The Court removed the costs. Nine states took the opening in under a year.

If the problem is that the people who benefit from maps are the ones drawing them, the fix is to take the pen out of their hands. Eight states hand redistricting to independent commissions.^[19] They produce more competitive races than maps drawn by the party in power. Of the nineteen House seats that changed party in 2024, thirteen came from fairer processes. Five were drawn by independent commissions, five under court supervision, three by a divided legislature.^[20]

California created an independent citizens' commission by popular vote. Voters suspended it by popular vote when the political incentive was strong enough.^[16]

The Fair Representation Act, introduced repeatedly by Rep. Don Beyer since 2017, would go further. It calls for multi-member congressional districts of three to five seats, elected by ranked choice voting, with maps drawn by independent commissions.^[21] With multiple seats per district and a roughly 20 percent election threshold, gerrymandering becomes far harder to execute. The bill has never passed committee.

The people who draw the lines choose who wins. That incentive has outlasted every guardrail erected against it. As long as the pen is worth holding, someone will reach for it.