RUTLAND, N.D. — When Senator Heidi Heitkamp, a Democrat, and her Republican opponent, Representative Kevin Cramer, put Sunday’s annual Uffda Day celebration on their schedules this year, they most likely thought they would get an earful from voters about tariffs here in the heart of North Dakota’s soybean belt.
But the Scandinavian food festival in this town of 155, a fixture on North Dakota’s political calendar, instead served as a snapshot of the nation’s changing electoral landscape, illustrating why the Senate majority leader, Mitch McConnell, was so eager to ram through Brett M. Kavanaugh’s Supreme Court nomination ahead of the midterm election.
Voter after voter brought up the polarizing Supreme Court battle to the two candidates as they made their way around the lefse and other Norwegian delicacies; the comments reflected the country’s divide, with Republicans thanking Mr. Cramer for standing by Justice Kavanaugh and Democrats offering hugs to Ms. Heitkamp to show their appreciation for her opposition.
The intense interest, even in a farm-focused state far from Washington, reflects the extent to which the partisan divide over Justice Kavanaugh has transformed the political debate in just a matter of weeks. With less than a month to go until the election, the battle for control of the Senate has been nationalized by the showdown over the Supreme Court, and for the moment has left Democrats alarmed and Republicans elated.
The news could shift quickly in the month before the election; change is perhaps the only constant in the Trump era. But in a year in which crucial Senate races will play out in a series of heavily rural states that President Trump carried, a riveting, made-for-television clash over gender, politics and privilege is hardly what Democrats like Ms. Heitkamp had hoped would frame the final stretch of the election.
“The smart political vote would have been to vote for Kavanaugh,” Ms. Heitkamp said after marching in a six-block parade here, acknowledging that her opposition would anger some of the state’s voters and that she’d rather focus on trade and tariffs, “not a Supreme Court nomination.”
But, Ms. Heitkamp said, “that’s the way it just goes.”
Republicans, for their part, not only delivered a conservative majority on the Supreme Court but galvanized conservative-leaning voters in a campaign that previously had been dominated by a surge in Democratic enthusiasm.
“There is nothing that unifies all stripes of Republicans more than a court fight,” Mr. McConnell said in an interview, adding: “They stupidly handed us the best issue they possibly could going into the fall election. And it totally underscores the importance of keeping a Republican Senate.”
There are real risks for Republicans. Seating a man on the nation’s highest court who was accused in searing terms of sexual misconduct has only enraged many women who were already eager to register their contempt for Mr. Trump at the polls. And it may further imperil the party’s tenuous House majority and its prospects in a handful of big-state governor’s races that could turn on anti-Trump energy.
But the terms of the debate have shifted profoundly for Democratic Senate candidates.
From North Dakota and Missouri to Montana and Tennessee, they have been trying to localize races, either ignoring Mr. Trump or highlighting their willingness to work with him while playing down the court fight and emphasizing regional issues.
In Montana, Senator Jon Tester and his allies have been assailing his Republican opponent, Matt Rosendale, a Maryland native, as an East Coast real estate developer. In Missouri, Senator Claire McCaskill has taken every chance to highlight the Ivy League and law professor background of her challenger, Josh Hawley.
At the same time, Phil Bredesen, the Democratic Senate nominee in Tennessee, has done just about everything he can to distance himself from national Democrats. He has spent much of his campaign talking about his tenure as governor and as Nashville’s mayor, and even tried to inject the invasion of Asian carp in the state’s waterways as an issue in the race.
And Ms. Heitkamp has portrayed herself as a champion of North Dakota’s farmers and ranchers, recording ads of herself standing in knee-high soybean fields.
Now, though, Republicans in these races are using the court clash to turn the campaign into more of a national referendum on the fate of their 51-49 majority and a test of which side the voters are on: that of Mr. Trump and Justice Kavanaugh or the angry Democratic opposition.
“I hope the battle cry of Republicans for the next 30 days will be ‘Remember Kavanaugh,’” said Senator Charles E. Grassley, the Judiciary Committee chairman, at a Republican dinner Sunday in Iowa.
Mr. Cramer, referring to his state’s electorate, said that “280,000 people are going to decide something that’s got very significant national implications,” adding that the Kavanaugh showdown demonstrated “with great clarity what can happen if those crazy people get control of the government.”
Mr. Cramer as well as the Republican candidates in Missouri and Indiana repeatedly invoke the Senate Democratic leader, Chuck Schumer, when they criticize their rivals for opposing Justice Kavanaugh, and Mr. Rosendale has even unveiled a commercial linking Mr. Tester’s vote to the protesters who are confronting Republicans in restaurants and other public spaces.
What concerns Democrats is that the elevation of national issues, and particularly the Supreme Court, which is so easily linked with abortion and other cultural flash points, may exacerbate their difficulties in rural America.
And Mr. Trump, in part because Republican candidates do not want him campaigning in major cities or moderate suburbs, is compounding the Democrats’ dilemma by repeatedly touching down for rallies in smaller, heavily conservative regions.
The Democratic candidates in red states do not need to win most, or even a majority, of the less-populated areas of their states. But as was demonstrated vividly in Hillary Clinton’s 2016 loss, they cannot afford to get trounced there.
“The secret to winning Missouri is you’ve got to do well in the urban centers and you cannot get your clock cleaned in rural Missouri,” said Roy Temple, a former state party chair there, citing a maxim from the state’s former governor Mel Carnahan. It’s a lesson that applies to nearly all the states Democrats must win this year to reclaim the Senate majority.
Democrats from heartland states are also infuriated by what they see as the self-defeating claim from coastal liberals that rural whites simply cannot be won over.
As recently as 2010, they point out, three of the four senators from the Dakotas — as well as the six senators in West Virginia, Arkansas and Montana — were Democrats.
“We’ve got to have a 50-state strategy because we’re not going to win a durable Senate majority if we give up the heartland,” said the former North Dakota senator Byron Dorgan, a Democrat who is quick to note he won 11 statewide races here. “We have to compete everywhere.”
But Mr. Dorgan was uneasy about the specter of Ms. Heitkamp’s race evolving into a debate on the Supreme Court.
The question, he said, is “will this be a race about partisan, tribal politics or does retail politics still work in North Dakota?”
Asked in an interview over coffee in Bismarck what would happen if the campaign becomes a test of red-versus-blue loyalties, Mr. Cramer did not hesitate: “She’s toast,” he said of Ms. Heitkamp, adding, “But she’s done her best to try and make it not that.”
Ms. Heitkamp, however, plainly recognizes the peril in her vote against Justice Kavanaugh.
She immediately taped and began airing a commercial in which she directly addresses the camera and notes she voted for Justice Neil M. Gorsuch, adding that “there are many conservative judges who can fill this job without tearing our country apart.”
Her choice was “a lose-lose proposition,” said the state attorney general, Wayne Stenehjem, a Republican, noting that she would have deflated her base had she supported Justice Kavanaugh but that a majority of voters here clearly supported his confirmation.
In Bismarck, the Republican-leaning state capital, interviews with voters at two breakfast hubs Saturday illustrated what a political bind Ms. Heitkamp was in.
Outside the Little Cottage Cafe, Lee Klein, a retired insurance executive who supports Ms. Heitkamp and called Mr. Cramer “a weasel,” was blunt about what he thought the consequences would be for Ms. Heitkamp.
“That vote today is going to sink her,” said Mr. Klein, who wrote in Harry S. Truman for president in 2016, pointing to “the polarization of the parties.”
At Terra Nomad, more of a scone-and-latte setting, four women who try to avoid talking politics and did not want to share their names with a reporter were divided: One said she would have been disappointed had Ms. Heitkamp supported Justice Kavanaugh while another said she would grudgingly support Mr. Cramer because of the senator’s vote.
In Rutland, a historically Democratic corner in the southeastern part of the state — bulwark of Ms. Heitkamp’s 3,000-vote victory in 2012 — many voters thanked the senator for her opposition to Justice Kavanaugh.
The senator’s brother, Joel Heitkamp, however, acknowledged how challenging it would be to run a national race here.
“I can sit here and lie to you about it and say it’s not a big deal but it’s a big deal, it’s a really big deal,” said Mr. Heitkamp, a former state legislator from this area who now has his own radio talk show. “Our hope is that people see it, they appreciate it for the honesty it was and they move on to the overall message of being anti-tariff and pro-farmer.”
North Dakota was once a pillar of prairie populism, flirting with socialism and creating a state bank and a state mill that still exist today. Only a decade ago it sent three Democrats to Congress and gave Barack Obama 45 percent of its vote. Since then, however, it has seen its Democratic Party hollow out, losing legislative seats, including in this region, and giving Hillary Clinton just 27 percent.
“People think the Democrats have focused too much on culture, and culture that doesn’t reflect their values,” Ms. Heitkamp said of her state’s voters.
The senator conceded she was trailing at the moment, but she and Republicans here were skeptical she was down by the double-digit margins some public polls have indicated.
“This isn’t over yet,” she said.
Sydney Ember contributed from Waterloo, Iowa, and Nicholas Fandos from Washington.