At President Donald Trump's urging, Republicans pursued an unprecedented mid-decade redistricting campaign ahead of November's midterm elections, redrawing dozens of US House of Representatives districts in an effort to preserve their narrow majority.

With less than two weeks until Election Day, however, Trump's unpopularity has wiped out most of those gains, leaving Republicans scrambling to defend even districts they engineered to be safely conservative.

As of June, Republicans had increased their advantage in 16 redrawn districts. Today, nine of those Republican-leaning districts are either expected to go to Democrats or are too close to call, according to a Reuters analysis of ratings from leading election forecasters. A 10th Republican district was thrown out by courts.

Redistricting typically occurs only once a decade following the US Census' population count. But Texas Republicans tore up the state's existing US House map last summer with Trump's backing, setting off a multistate fight between the parties that Republicans appeared to win handily. Democrats were only able to use redistricting to gain an edge in six districts.

But what looked like a Republican victory has since been undercut by Trump's record-low approval rating, driven by the unpopular war in Iran and Americans' deep frustration with the resulting high gas prices.

"It's a powerful lesson that you can be too smart for your own good when you try to predict the future," said Michael Li, a redistricting expert at New York University's Brennan Center for Justice.

Most of the Republican gains were expected to come from Texas and Florida, where new maps reshaped nine Democratic-held seats into districts that Trump carried in 2024 by anywhere from 9 to 20 percentage points.

But the collapse of Trump's support among Latino voters has upended the political calculus in those states. Analysts now view only one of those nine as a sure thing for Republicans, with six considered highly competitive.

"I think the maps in Texas and Florida were way too confident that Hispanic voters would continue to vote for Republicans at the same level they did in 2024," said Erin Covey, who analyzes US House races for the Cook Political Report. "There is absolutely a world where Republicans don't flip any of the four seats they redrew in Florida." The median outcome for Republicans is a gain of around three seats from redistricting alone, Covey said. But if the Democratic wave turns into a tsunami, she added, Democrats could actually end up netting two seats through redistricting.

That said, the national House map is objectively better for Republicans than it was prior to redistricting, according to Jacob Rubashkin, an analyst at Inside Elections.

"The number of pickups is almost certain to fall well below expectation," he said. "It's also true that Republicans will still do better because they redistricted than had they lived and let live." Some of the newly redrawn districts are among the races that have drawn the most campaign spending, underscoring their competitiveness. Four of the six House races that have received the most outside spending from Republican-aligned groups - an average of more than $12 million each - are taking place in Republican-redistricted seats, according to campaign finance data.

Democrats need to flip at least four House seats on November 3 to win control of the chamber. Even districts that once seemed unassailable are potentially in reach for Democrats.

After the US Supreme Court in April hollowed out the Voting Rights Act's protections for districts with large minority populations, Alabama Republicans quickly dismantled one of the state's two predominantly Black districts in favor of a new, majority-white one that backed Trump by more than 14 percentage points in 2024.

But now, two national forecasters, Inside Elections and Sabato's Crystal Ball at the University of Virginia, both categorize the race as "Lean Republican," suggesting incumbent Democrat Shomari Figures could prevail in a strong Democratic wave.

To be sure, Democrats may not carry every seat they redrew either. In California, where Democratic lawmakers passed a new map targeting five Republican-held seats, two Republicans are locked in tight contests with Democratic challengers, according to analysts.

In some cases, the new maps could also have unintended consequences for incumbent Republicans.

Under the updated Texas map, the seat of Republican Monica De La Cruz remained solidly Republican, with Trump winning the district's voters by nearly 18 percentage points. But most of that territory was new to her, forcing the incumbent to introduce herself to swaths of new voters.

Her Democratic opponent, Bobby Pulido, is a well-known Tejano music star who has sought to transform his cultural popularity into political success. That seat is now widely seen as a tossup.