The number of competitive US House of Representatives districts in this fall’s midterm elections was already near historic lows before the US Supreme Court’s decision on Wednesday opened the door to even more aggressive efforts to draw district lines for political gain.

The court’s ruling, which arrived amid what was already an unprecedented national fight over congressional redistricting, may usher in a new era of nakedly partisan gerrymandering ​that results in still fewer competitive elections, leaving voters with less power than ever, experts said.

The lack of competitive races means that control of the US House of ‌Representatives will likely be determined in November's midterm election by fewer than 10 percent of Americans, with the winners in the vast majority of districts all but assured before a single ballot is cast, a Reuters analysis found.

Only 32 of the House’s 435 seats are currently considered competitive, according to the analysis. Those districts were rated either toss-ups or leaning toward Democrats or Republicans by three leading independent forecasters: Cook Political Report, the University of Virginia’s Crystal Ball and Inside Elections.

Most other districts ​are simply out of play. Cook, for instance, rates 375 seats, more than 85 percent of the House, as either “Solid Republican” or “Solid Democrat,” which means its analysts do not expect them to be ​seriously contested. Another 28 races are “likely” Republican or Democratic, according to Cook, meaning they are not competitive at present but might become so under new conditions.

This year boasts the fewest competitive House races at this stage of the election cycle since at least 2008, according to an archive of prior Cook ratings.

Democrats need to gain just three seats to win ​a House majority, giving them the power to block President Donald Trump’s legislative agenda and initiate investigations into his administration.

The shrinking House battlefield is the result of several factors, including increased political polarisation. But the weaponisation ​of congressional redistricting, or gerrymandering – which has gone into overdrive since last year, when Trump began pushing Republicans to draw new maps – is a critical element that is only going to accelerate after the Supreme Court’s ruling, according to experts.

“We are now in a cycle of gerrymandering wars,” said Justin Levitt, a professor at Loyola Law School who maintains the website All About Redistricting. “What used to be a cold war has gotten very hot.”

The court hollowed out a provision of the federal ​Voting Rights Act that had blocked state legislatures from dismantling districts with mostly racial minority voters. Political observers expect Republican-led states to target a dozen or more Democratic-held majority-Black and majority-Latino seats that previously enjoyed stauncher ​protections.

“I think it gets worse before it gets better,” Levitt said. “And I think there’s plenty of room for it to get worse.”

‘No Guardrails’

The lack of competitive districts can have consequences for Congress, said Matthew Klein, a House analyst ‌with Cook. If ⁠House candidates only need to appeal to their base voters to win elections, rather than moderates or members of the opposing party, they are more likely to move toward the extremes instead of the political middle.

“If you look at Congress and how it acted 20 years ago, 30 years ago, even farther back, you see a Congress that is both less acrimonious and also more productive,” he said. “There used to be bills that passed with huge majorities on major issues. We just don’t really see that anymore.”

Gerrymandering has long been a feature of American democracy, but the practice has been supercharged in recent years as guardrails, both legal ​and institutional, have been torn down. In 2019, ​the Supreme Court found that while partisan gerrymandering may be undemocratic, federal courts had no role in regulating it.

Last year, Trump successfully pressured Texas Republicans to rip up their map and draw a new one targeting five Democratic incumbents, triggering a nationwide arms race that spread to nearly a dozen other states. That move eviscerated what had been a traditional norm ​limiting most redistricting to the start of each decade, after the US Census population count is completed.

The Supreme Court’s ruling on Wednesday, meanwhile, has given ​even more leeway to lawmakers ⁠to draw districts for their party’s benefit. And all of those developments have come against a backdrop of technological advances, with mapmakers able to identify Democratic and Republican voters down to the census block.

“If there are no guardrails, there are no guardrails,” Levitt said. “I think the constraint is now realpolitik and imagination, not, ‘We just don’t do that.’”

Gerrymandering is not the only culprit to blame for the lack of competitive districts. Voters have become more geographically sorted, as rural ​areas have trended conservative while suburban regions moved left.

And just as House members have become more polarized, so too have voters. ​Split-ticket voting, in which voters choose a candidate of one party for a higher office and another for a lower office, was once fairly common, but no longer.

In 2000, there were 86 House members elected whose districts voted for the opposing party’s presidential ​candidate, according to research by Kyle Kondik, the managing editor of Crystal Ball. In 2024, that number was down to 16.