How the Supreme Court greenlit America's gerrymandering battle

A clutch of southern Republican-led states have this year redrawn their election maps ahead of November's midterm elections at the urging of President Donald Trump.

The gerrymandering rush was prompted by a US Supreme Court ruling that will make it harder for voters to challenge new maps in federal court. The case, Louisiana vs Callais, centres on the 1965 Voting Rights Act, a civil rights era law that sought to end race discrimination in the electoral system.

Maps are normally redrawn once a decade after a census and typically not too close to an election. But the president wants to change that in an attempt to tip the electoral balance in his Republican Party's favour.

Trump started an arms race last year by pushing Texas Republicans to redraw that state's maps mid-cycle, and the Democrats responded by redrawing maps in states that they controlled.

In the longer term, new maps could lower African American representation and reduce the election of Democrats in Republican states and vice versa.

What is the Voting Rights Act and why does it matter?

The landmark civil rights era law is rooted in the Fifteenth Amendment to the US constitution, which in 1870 said citizens could not be denied the right to vote because of their race. It gave Congress the power to enforce the principle using legislation.

But Black votes were for decades suppressed through gerrymandering and onerous requirements such as literacy tests and property qualifications, culminating in the brutal 1965 attack by authorities in Selma, Alabama, on non-violent civil rights protesters marching to secure voting rights.

Later that year, Congress passed the Voting Rights Act, Section 2, which ruled states should not curtail voters' rights on account of race.

The act was a way to challenge gerrymandering that diluted the impact of Black voters, often done by "packing" and "cracking". Packing means cramming large numbers of Black voters, who tend to vote for Democrats, into a single district so that only one Democrat is elected rather than two or more; cracking is splitting a Black community across several districts so that their votes are drowned out by white Republican voters.

The Callais ruling has "essentially gutted" that part of the act, said Sarah Brannon, deputy director of the American Civil Liberties Union's Voting Rights Project.

A 1982 amendment to Section 2 said the law would be violated if election processes based on the "totality of circumstances" meant Black voters had less opportunity to elect representatives of their choice than white voters. A 1986 Supreme Court ruling reinforced this, saying Section 2 might be violated if a district map meant that a large, geographically compact, politically cohesive group of Black voters could not elect a representative of their choice.

That led to a surge in the creation of "majority-minority" districts designed to ensure that Black voters in southern states could secure a level of political representation. Some of America's best-known Black politicians, including the late civil rights activist John Lewis, have represented southern majority-Black districts.

But majority-minority districts were challenged in the courts, with some saying it was dangerous to organise voters by race because it risked entrenching stereotypes and deepening racial divisions. Such districts could also be geographically illogical.

The Supreme Court in 1993 ruled that classifying voters by race could be harmful and states would need a strong justification to do so when drawing districts.

The court in 2019 made it easier to gerrymander for purely political purposes. It ruled that such changes were not something federal courts could intervene in because the constitution did not give them the authority to decide what they said were political questions.

What was challenged in the Callais case?

After the 2020 census, Louisiana redrew its congressional districts. In 2022 a judge said the new map likely violated section 2 of the VRA because it did not create a second majority Black district.

The state redrew its map, creating in 2024 a district that streaked diagonally across the state, connecting Black voters in Baton Rouge with those roughly 250 miles away in Shreveport. A roughly equivalent-looking UK map would put London and Liverpool in the same district. The unusual shape helped protect the seats of top Republicans including House Speaker Mike Johnson and House majority leader Steve Scalise.

That map was challenged almost immediately by a group of mostly white voters, led by Phillip "Bert" Callais, a man described in court filings as a "non-African American voter who resides in Brusly, Louisiana". They said the map denied them the right to elect a representative of their choice. They won in lower courts, but the state appealed, leading the case to the Supreme Court.

The Supreme Court justices voted 6-3, largely along ideological lines, in favour of Callais. "No compelling interest justified the state's use of race in creating [the new district], and that map is an unconstitutional racial gerrymander," the majority ruled.

One impact of the ruling is that it will be far more difficult for voters to challenge new maps that dilute the impact of Black voters in southern states, including by dismantling existing majority-Black districts. To succeed, they will have to show the map was created with race rather than partisan interests in mind.

"We will not be able to bring successful section 2 cases," said April England-Albright, national legal director of the campaign group Black Voters Matter. "Virtually unless you have them saying, we are doing this because they are Black, you cannot win this case."

The ruling will end the creation of districts designed with race in mind, for example to enable Black or other minority voters to elect a candidate of their choice.

Clarence Thomas, one of the Supreme Court's two Black justices, wrote in support of the ruling, saying such measures had divided the country along racial lines in ways he found unacceptable.

But his fellow justice Elena Kagan wrote in a dissent that the ruling has "laid the groundwork for the largest reduction in minority representation" since the years that followed the civil war.

Will the ruling affect the midterms?

The full impact of the map changes is uncertain, but the Callais ruling has at least "increased the chances that Republicans will hold on to the House", said Benjamin Schneer, associate professor of public policy at Harvard Kennedy School.

He added gerrymandering ahead of the November vote could create 10 more seats that the Republicans are likely to win even with the Democrats redrawing their own electoral maps mid-cycle.

But it could also result in so-called "dummymandering" where, for example, an attempted Republican gerrymander in the South could backfire by spreading Black voters among other districts in a way that, combined with a large swing, leads to more Democrats being elected.

Non-partisan election forecasters say Democrats are likely to retake the House given Trump's declining approval ratings and the historical trend of the party out of power making gains in midterm elections.

But in the longer term, the Callais ruling, combined with the Supreme Court's 2019 decision that keeps federal courts out of political gerrymandering issues, might unleash unrestrained gerrymandering by both parties.

Schneer said "maximising gerrymanders everywhere would roughly cancel each other out", producing a House of Representatives whose total number looks similar to today.

But the breakdown would be very different, with more states having representatives only from one party, making the House election map look more like the electoral college where the dominant party takes all.

However, it would be harder for Democrats to gerrymander because many of their states have independent commissions or other measures limiting the practice, so Republicans would probably have "a bit of an edge in the longer run", Schneer added.

Are there any obstacles to further gerrymandering?

There are some. State courts can intervene and could become a more significant forum for contesting claims of racial and partisan redistricting.

Some state legislatures have laws banning partisan gerrymandering and some state constitutions ban redistricting outside the post-census period.

There is also resistance to redrawing electoral maps even among Republicans: in Indiana, party representatives last year voted against redistricting and the state senate has declined to take up a new map in time for the midterms.

Campaign groups are actively trying to prevent redistricting: the National Association for the Advancement of Colored People is asking Black athletes and fans to withhold athletic and financial support from public universities in southern states that they say are "attacking Black voting rights".

The Black Votes Matter group is campaigning to raise turnout in response to the gerrymandering. "Eighty-nine million people did not vote in the presidential election; that's more people than voted for either side," England-Albright said.

"So we've got to awaken folks . . . if everyone comes out, we could capture these seats even in districts that they are trying to take away from us."