The nomination fight over Judge Brett M. Kavanaugh has injected new volatility into the midterm elections, reshaping races across the country and sharpening the already bitterly partisan tone for the final four-week stretch before Nov. 6.

Much uncertainty remains — not least because of the rapid-fire succession of evolving crises that have marked President Trump’s term in office — but for now the weeks-long Kavanaugh saga appears to be pushing House races toward Democrats, even as it has given Republicans better odds of maintaining control of the Senate.

That division stems from the makeup of the races and the political geography of the most competitive battles. House contests this year already were expected to be determined by suburban women, who had pulled away from the president over his term in the White House and appear to be the most sympathetic to Christine Blasey Ford, the woman who testified that Kavanaugh had assaulted her when both were teenagers.

But most of this year’s competitive Senate races are in traditionally red states, and as Republicans have rallied to Kavanaugh’s side, the chances of Democratic upsets there have dropped, at least for now.

Democrats are growing more concerned about keeping their seats in Indiana, Missouri, and Montana and appear to be losing ground when it comes to potential pickups in Texas and Tennessee. One of the most vulnerable Democratic incumbents, Sen. Heidi Heitkamp of North Dakota, who said Thursday that she would vote against Kavanaugh, has fallen far behind her Republican challenger in new polling. Sen. Joe Manchin III of West Virginia, another vulnerable Democrat, looked to secure his lead when he became the final senator and only Democrat to announce a vote for Kavanaugh.

But in the House, political prognosticators have moved more than half a dozen seats in the Democratic direction in recent days, and Republican operatives are bracing themselves for an onslaught of Democratic money that they are calling “a green wave.” Gubernatorial races — in which Democrats are trying to regain territory that they’ve lost in recent years, particularly in the Midwest — are also trending left.

“There’s nothing quite like a good old-fashioned Supreme Court fight to polarize the electorate — and that’s what we’ve observed in the past few weeks,” said David Wasserman, House editor of the nonpartisan Cook Political Report. “The Kavanaugh issue has almost acted as a centrifuge to separate red and blue elements of the electorate even more.”

The Supreme Court battle has washed over the campaign in a way that no single issue has before, drowning out topics Democrats want to talk about (health care) or the ones Republicans are pushing (tax cuts and a rosy economy). In a season defined by enough-is-enough female energy — along with white male rage and aggrievement that is stomping back to 2016 levels — the Kavanaugh confirmation hearings were explosive on all fronts.

In recent days, Trump has fiercely defended Kavanaugh and mocked his accusers, candidates have aired new ads on their positions, debates have pivoted on the nomination, and both parties have sensed political advantage in what already had stacked up as an election dependent on each side motivating its base.

The divide into separate camps has been on vivid display among protesters inside the U.S. Capitol — but it is also playing out more subtly in the rest of the country, from retail store parking lots in Fargo, N.D., to the bars of Bedminster, N.J.

Democrats have always faced a difficult Senate map — six of the competitive seats that they hold are in states Trump won, and five of those states he carried by at least 19 points — but their path now is more treacherous.

In North Dakota, television screens across the state were flashing with ads both attacking Heitkamp and defending her record. At Fargo’s VFW Post 762, drinkers pulled their eyes away from the nightly happy hour drink raffle to watch back-to-back political spots.

Just hours before Heitkamp announced her opposition to Kavanaugh, voters like Stephanie Beyah were still weighing their support for the incumbent based on what the senator might do.

“I think it would be awful [to have Kavanaugh on the Supreme Court],” Beyah, a young woman in her 30s, said as she pushed a cart of purchases through a Targetparking lot. “Just beyond the allegations, the way he portrayed himself last week was terrible. This is not a spot on the school board. You’re choosing a guy that will change people’s lives.”

Troy Reich, a burly man in a flannel shirt juggling a stack of boxes as he entered a post office in downtown Fargo, said he was a firm supporter of Heitkamp’s opponent, Republican nominee Rep. Kevin Cramer (R-N.D.). But the Kavanaugh hearings increased his anger at Democrats, and he feels the drama will affect tight races like the Senate contest.

“It was a total witch hunt,” Reich said. “I think it was ridiculous, and now they still haven’t proven anything. It was totally partisan, and I think it’s going to come back around on them.”

In Indiana, where Democratic Sen. Joe Donnelly is fighting for reelection in a state Trump won by 19 points, the Kavanaugh dispute has riled up conservative male voters who feel he is a victim of partisan smears and unfounded accusations about what amounts to schoolboy antics, said Brian Howey, the author of a website on Indiana politics.

“The allegations of Dr. Ford, they just threw a pipe bomb in this race,” Howey said. “Now we’re waiting to see who the shrapnel takes out.”

Recent polls show a dead heat between Donnelly, who announced his opposition to Kavanaugh last month, and his Republican opponent Mike Braun.

Tim Chapman, the executive director of Heritage Action for America, a conservative political organization, said the Kavanaugh hearing was a “game changer” for red state Democrats like Donnelly.

“He is in a really tough spot,” Chapman said. “He is going to vote against Kavanaugh, so for us, that becomes a real issue that we can drive from now until November and remind people that he was on that side.”

Kate Oehl, Donnelly’s press secretary, said the senator will spend the next month focused on health care, which his campaign believes is a more salient issue for voters.

For Republicans, a major challenge will be keeping their base riled up over how Kavanaugh was treated, even though he was confirmed in the end.

Democrats believe the Kavanaugh hearings could help them in Nevada — where Rep. Jacky Rosen is running against Republican Sen. Dean Heller for his seat — and in Arizona, where Rep. Kyrsten Sinema (D-Ariz.) and Rep. Martha McSally (R-Ariz.) are in a tight race to succeed Sen. Jeff Flake (R), who opted not to run again.

The dynamics in the House races are completely different because of their political terrain. Of the 68 House races viewed as competitive by the Cook Political Report, only 16 are in states that have a competitive Senate race.

“That’s unheard of,” Wasserman said. “We just have this huge divergence between the partisanship of the most competitive Senate seats and House seats.”

Democrats are feeling confident about winning a net of 23 seats needed to control the House. Already, Republicans are pulling money from several districts they had initially hoped could be within their grasp.

Republicans are suffering particular problems among highly educated voters who live outside urban centers like Kansas City, Philadelphia and Denver.

The National Republican Congressional Committee pulled about $1 million in planned spending from the 3rd Congressional District in Kansas, where Rep. Kevin Yoder is running for reelection. Outside groups on both sides have also been pulling ads from districts like those held by Reps. Barbara Comstock (R-Va.), Mike Bishop (R-Mich.) and Mike Coffman (R-Colo.), an indication that they no longer see those races as competitive.

“If the Democratic base gets any more excited they may have to seek medical attention,” said Corry Bliss, who runs the Congressional Leadership Fund, which is aligned with House Speaker Paul D. Ryan (Wis.) to preserve the House GOP majority. “In the last week things have undeniably improved in our polling. Republican intensity and excitement are through the roof. Now we need to keep the trend going for the next few weeks.”

The countervailing forces could be seen in the suburbs outside of Newark, where Republican Leonard Lance is seeking his sixth term in a district that Hillary Clinton carried in 2016.

“It’s been a re-energizer, frankly,” Janice McLean, 58, said during a Democratic-led protest in New Jersey.

“Republican women are motivated,” said Marlene Sincaglia, a retired middle school French teacher, a few hours later and a few miles away.

Lance’s opponent, Democrat Tom Malinowski, a former assistant secretary of state under President Obama, released an ad on Sept. 26 featuring a sound bite of Lance seeming to question Ford’s allegations that Kavanaugh had assaulted her.

“I think Judge Kavanaugh is a brilliant judge and I tend not to believe the charges,” Lance is heard saying on the clip.

Lance told The Post he found Ford’s testimony to be credible — as well as Kavanaugh’s — and noted that he was among the Republicans who called for an FBI investigation.

Protesters, who have often come to his district office to protest Trump, are now focused on Kavanaugh.

In Westfield, N.J., days ago, a 2-year-old girl on her father’s shoulders held a message scrawled on the back of a Pampers box: “Believe Women.” A 61-year-old artist waved a fluorescent pink sign that said “Hell No Kava-No” in her left hand and a tambourine in her right. Another woman who said her college-age daughter had been raped her freshman year propped up a banner that read “I Believe Dr. Christine Blasey Ford!”

Across the district in Berkeley Heights, Lance mingled with constituents nibbling on crudités at a reception before kicking off a Boy Scouts awards dinner. Some of the Republican voters there were fired up — in support of Kavanaugh.

“I look at this and I fear for my 20-year-old son,” said Jeanne Kingsley, a Berkeley Heights councilwoman who is a Republican and mother of two sons and two daughters. “I called him and said, ‘Do not be alone with a woman. We’re in an environment now where someone can say anything they want and not have to back it up.’”

Margaret Illis, another woman at the event, has two sons and two daughters spanning ages 17 to 24. It is her daughters she fears for.

“I don’t know a single woman in my generation who wasn’t in some way sexually assaulted, whether it was being felt up on the train in New York City or by a boss at a fast-food restaurant when you were 16 or a co-worker who continually got too close in the elevator,” said Illis, 59-year-old former designer and analyst for a software development firm. “I really thought the world had changed. And now I’m opening my eyes to the fact that it hasn’t.”

Illis, a recently registered Democrat who considers herself an independent, said she has voted for Lance a number of times in the past. She now plans to vote for Malinowski because “I want my daughters to have a better future.”

“After the Kavanaugh hearings, people are resolved to do more to try to flip the House,” said Illis, who attends house parties where activists send handwritten notes to infrequent voters encouraging them to vote by mail and reminding them of what’s at stake.

“I’m passionate now,” she said, “about changing my representative in Congress.”

Laura Meckler contributed to this report.