Just two weeks ago, Democrats felt increasingly emboldened about taking control of the House in November after seeming to fight the redistricting wars to a draw.

But two court rulings — one by the Supreme Court and another by Virginia’s top court — and an aggressive new push by red states to carve up congressional maps have delivered the Republican Party its biggest burst of momentum in many months.

Put bluntly, Republicans have roughly 10 more House seats that favor them than they did just 10 days ago, and Democrats are suddenly grappling with a new landscape.

“This is now clearly closer than it was just a week and a half ago,” Representative Brendan Boyle, a Pennsylvania Democrat, said of his party’s chances to retake the House.

Democrats are still widely seen as favored to win the House this fall. Republicans face a daunting political climate, saddled with President Trump’s sagging approval ratings, high gas prices and an unpopular war with Iran. In special elections and last year’s races for governor, Democratic enthusiasm has swamped Republican turnout.

“I was anticipating about a 15-to-20-seat pickup before the last week and a half,” Mr. Boyle said. “Now I would be anticipating a 10-to-15-seat pickup.”

That would be more than enough to wrest the majority from Republicans, who are clinging to a current edge of 217 to 212 seats. And history is not on Republicans’ side: The party in power almost always loses seats in midterm elections.

But after the latest map changes, winning the House majority will require Democrats to flip more seats in less hospitable territory.

Bullish Republicans feel they are back in the game.

“Lord grant me humility,” James Blair, the Republican strategist who is overseeing Mr. Trump’s political operation in the midterms, wrote on X on Friday after Virginia’s top court struck down a recently enacted map meant to give Democrats four extra House seats.

One of Speaker Mike Johnson’s senior political aides interrupted the middle of a meeting in Texas, where the Republican leader was on a fund-raising swing, to break the news, according to two people with knowledge of the conversation. Mr. Johnson later celebrated on the phone with Glenn Youngkin, the former Republican governor of Virginia, who had opposed the Democratic effort to redraw the state’s lines.

The last 10 days demonstrated the power and speed of the courts to shape the midterms — and the role of judges in the next phase of the redistricting battle. Recent legal actions are underway in Virginia, Tennessee, Florida, Louisiana and Alabama that could still undo or block some of the potential Republican gains before the fall.

The outcome of the legislative and legal fight, which has unfolded largely beyond the control of American voters, could be highly consequential. No party has made a net gain of more than a dozen House seats in a national election since the wave of 2018.

Representative Yvette D. Clarke of New York, the chairwoman of the Congressional Black Caucus, said in an interview that Democrats were engaged in “meetings on meetings on meetings” on Friday to figure out how to respond in Democratic-controlled states. But the party’s next steps were unclear, she said, noting that some potential paths seemed to be closed because of the election calendar.

“It’s not,” Ms. Clarke said, “a good feeling.”

A Flood of Good News for Republicans

The last few weeks stand as a remarkably important period in the battle for Congress this fall.

On April 21, Virginia voters narrowly passed a referendum to approve a newly gerrymandered, Democratic-drawn map. Soon after, Representative Hakeem Jeffries of New York, the top Democrat in the House, held a news conference where he repurposed a slogan first used by a person close to Mr. Trump last year in The New York Times: “Maximum warfare, everywhere, all the time.”

“Republicans launched this gerrymandering war,” Mr. Jeffries said. “And we’ve made clear as Democrats that we’re going to finish it.”

But the battle was just beginning.

Just over a week later, the Supreme Court dropped a major ruling on the Voting Rights Act that unraveled decades-old protections for Black voters in the South. The decision opened the door for Republican-led states to rip up their maps and dilute Black voting power across multiple districts, effectively creating new G.O.P. seats.

The very day that the Supreme Court issued its ruling, state legislators in Florida adopted a new congressional map that created up to four additional Republican-leaning seats. “Signed, Sealed, and Delivered,” Gov. Ron DeSantis, a Republican, wrote on social media the next Monday as he signed it into law.

Aiming to press forward with a redistricting offensive that Mr. Trump started, more Republican-led states are considering similar changes. The party’s lawmakers were reminded of the high price of refusing the president’s demands on Tuesday, when a group of Republican legislators in Indiana who had resisted his redistricting push lost their primaries to MAGA-backed challengers.

Then came Virginia, the biggest surprise of them all.

Add all the seats up where Democrats lost or could lose ground — up to four seats in Virginia, up to four in Florida, one or two in Louisiana, one in Tennessee, one in Alabama — and the total gives Republicans renewed optimism. Voters, of course, do have the final say, and Democrats are still aiming to flip two Virginia seats and compete in some of the new Florida districts.

Chris Pack, a Republican strategist, said that those predicting a Democratic majority with confidence in 2026 were doing so prematurely. He pointed to his work for the House Republican campaign arm in 2020, when the party beat expectations to pick up seats even as Mr. Trump lost re-election.

“Everybody counted Republicans down and out in that cycle, and they’re doing it again now,” Mr. Pack said. “When given the chance, Democrats like to step on the rake.”

Gearing Up for November

Both parties are now bracing for a district-by-district fight this fall.

Lis Smith, a Democratic political strategist who has worked with some of the party’s House candidates this year through a group called the Bench, said the latest changes to congressional maps only emphasized how hard-fought the election would be.

“Rather than navel-gazing and hand-wringing, we just need to focus on what will put us over the top here,” Ms. Smith said, “which is educating voters not just about Trump, but what his enablers in Congress have done.”

Chris Winkelman, the president of the leading House Republican super PAC, the Congressional Leadership Fund, derided the Democratic path to a majority as “an expensive house of cards.”

“As they wake up and realize they are overextended, they will find us well-resourced and locked into the core of the battleground,” he said.

At the end of April, the Cook Political Report, which handicaps political races, listed 217 House seats as at least leaning Democratic — meaning the party would have needed to win just a single “tossup” race to seize the majority. As of Friday, Cook rated 208 seats as at least leaning Democratic — meaning the party would need to win 10 of the 18 “tossup” races.

The final maps are still in flux less than six months before Election Day, with Democratic-aligned legal challenges underway to new Republican maps and redistricting efforts in Florida, Louisiana and Tennessee. And more Republican-led states, including Kansas, Alabama and South Carolina, are openly considering pressing for new maps.

Democrats in some blue states where redistricting efforts had previously been considered are searching for answers or possible new moves.

“I’m afraid for my party,” said State Senator Arthur Ellis of Maryland, a Democrat who has been calling for the state to redraw its map before the midterms, adding that losses in the gerrymandering war were creating a “real challenge” for the party’s efforts to reclaim the House majority.

Mr. Ellis said he planned to send a letter over the weekend to other Maryland state lawmakers demanding that they pass new district lines in response to the Virginia decision. “We all need to show the courage to stand up and to make our voices heard in this very crucial, critical stage in the history of the United States of America,” he said.

The Bigger Political Picture

Many Democrats remain confident that 2026 will still wind up as a wave year for the party and that Republicans will collapse under the weight of Mr. Trump’s unpopularity.

Jay Jacobs, the chairman of the New York Democratic Party, said that Republicans were still in “very rough shape” — and that their redistricting efforts could even backfire amid overwhelming Democratic enthusiasm.

“The longer gas prices remain high, the war in Iran continues and all of the other craziness is promoted by Trump, things will just get better and better as we get close to November,” Mr. Jacobs said.

Former Speaker Kevin McCarthy, Republican of California, said that House Republicans were “ecstatic” after the Virginia ruling, and that the gerrymandering war had turned out to be a “home run” for Mr. Johnson.

But he said that Democrats still had an advantage going into the midterm House races, and that the winnowing of the electoral map down to a small number of swing districts could cause lasting damage to American democracy.

“Any time you don’t allow the voters to pick their elected officials, that’s a recipe long-term for disaster,” Mr. McCarthy said.