The aftermath of the first presidential debate between President Trump and Democratic nominee Joe Biden triggered a reckoning among Republicans on Wednesday about the incumbent’s incendiary remarks on white supremacy and his baseless claims of electoral fraud, with GOP officials privately expressing alarm about the fallout with key voters as the president’s allies argued that he electrified his core supporters.

Biden, who launched a train tour through the battlegrounds of Ohio and Pennsylvania, continued to pitch himself as a champion of working-class voters and saw Democrats rally around what they view as Trump’s threat to American democracy.

But few Republicans voiced outrage in the wake of Trump’s norm-shattering spectacle in Cleveland on Tuesday, including his statement that the extremist Proud Boys, a male-only far-right group known for street violence, should “stand back and stand by.” Responses ranged from silence to muted criticism, reflecting how the GOP remains convinced that an alliance with Trump and his voters is crucial for its survival.

But hewing too close to him is also seen as a mistake by some Republicans, particularly for those who wish to court moderates and independent voters.

President Trump on Sept. 29 undercut assessments by the national security community and said violence mainly comes from far-left groups. (The Washington Post)

“There was fault on both sides,” Sen. Susan Collins (R-Maine), who is facing a tough reelection contest, told reporters on Wednesday. “The interrupting on both sides, the name-calling was very unbecoming for a presidential debate.”

Asked if it was a mistake for Trump not to condemn the Proud Boys and white supremacists, Collins said, “Absolutely.”

Sen. Tim Scott (R-S.C.), the lone Black Republican in the Senate, said he believed Trump “misspoke” and “should correct it.”

President Trump and former vice president Joe Biden spent time arguing and interrupting each other during the first presidential debate on Sept. 29. (The Washington Post)

“If he doesn’t correct it, I guess he didn’t misspeak,” Scott said.

The president told reporters Wednesday afternoon that he is unfamiliar with the Proud Boys group — which has white supremacist ties and sometimes employs nationalist rhetoricdespite seeming familiar with them on Tuesday night.

“I don’t know who the Proud Boys are,” Trump told reporters. “I mean, you’ll have to give me a definition, because I really don’t know who they are. I can only say they have to stand down. Let law enforcement do their work.”

Trump’s comments did little to encourage Republicans about the political turbulence they face in the final stretch of the campaign as Trump seizes on matters of race and urban unrest and unfounded allegations of voter fraud.

“This election is drifting toward what feels like a blowout [victory for Biden], and there needs to be some type of event that changes that. The debate was a chance to change the direction, and while it might be too early to be seen, there is no real reason to believe it was a game-changer,” said Brendan Buck, a former top adviser to the past two Republican House speakers, Paul D. Ryan of Wisconsin and John A. Boehner of Ohio.

Former senator Jeff Flake (R-Ariz.), a Trump critic who stays in touch with former colleagues, said the private alarm in Senate GOP circles “is palpable.”

“People are voting already, so they know it’s going to be tough to put forward a new narrative,” Flake said. “They’re more than a little worried because it feels like even if you go in a different direction, it’d be too little, too late. That’s devastating.”

Polling shows the GOP Senate majority at risk with strongholds in the Deep South, such as South Carolina and Georgia, highly competitive. A Quinnipiac University poll released Wednesday shows Sen. Lindsey O. Graham (R-S.C.) and former South Carolina Democratic Party chairman Jaime Harrison tied as Graham seeks a fourth term in the Senate.

One veteran Republican Senate strategist, who spoke on the condition of anonymity because they are working on a Senate campaign, said, “We’re all kind of prepared to be responsible for our own performances and our own words. You’re not going to see anybody say it was a bad performance, but they’ll consider it like Trump’s really crazy tweets. They’ll say, ‘That’s not my kind of campaign, didn’t really see it.’ ”

The strategist added that several campaigns are already deliberating on how to address Proud Boys questions at upcoming Senate debates and are trying to figure out how to deflect the issue and shift to more favorable topics.

At the Capitol on Wednesday, where Senate Republicans are working swiftly to confirm Trump’s Supreme Court nominee, Amy Coney Barrett, reactions ranged from venting about the debate to sidestepping challenges to Trump.

“It was awful,” Sen. Lisa Murkowski (R-Alaska) told reporters, while Sen. Ben Sasse (R-Neb.) offered a descriptive expletive.

“I was actually watching the Yankees,” said Sen. Mike Rounds (R-S.D.). When asked if he was disturbed by Trump’s response to the Proud Boys question, Rounds said, “He should have been very clear,” whether talking about “far-left” groups or “far-right” groups.

Sen. Thom Tillis (R-N.C.), who is in a difficult reelection race, said of Trump’s handling of the Proud Boys question: “I’ll leave it to the president. I know he’s not racist. I’m sure he doesn’t approve of their activities.”

Trump, however, remains confident that his bombastic approach is effective.

“There is no way that people want Joe Biden after watching that,” Trump told his aides after the debate, according to a Trump political adviser who spoke on the condition of anonymity to discuss private conversations with the president.

Speaking to reporters on Wednesday, Trump answered questions about white supremacy with calls on Biden to denounce leftist activists who have disrupted major cities.

“Joe Biden has to say something about antifa. It’s not a philosophy. These are people that hit people over the head with baseball bats,” Trump said, referring to loosely organized anti-fascist groups.

At a campaign stop Wednesday afternoon in Alliance, Ohio, Biden called Trump’s behavior during the first presidential debate “a national embarrassment” and said he hopes the Commission on Presidential Debates ensures that both candidates are allowed to speak without interruptions during their remaining two scheduled events.

“I just hope there’s a way in which the debate commission can control the ability of us to answer the questions without interruptions,” Biden told reporters. “I’m not going to speculate on what happens in the second or third debate. . . . But I’m looking forward to it.”

Asked what his message would be to undecided voters who were turned off from politics after watching Tuesday night’s debate, Biden responded, “I can understand it.”

“I kind of thought at one point — maybe I shouldn’t say this — but, the president of the United States conducting himself the way he did, I think it was just a national embarrassment,” Biden said. “Look, I just hope that the American people and those undecided voters try to determine what each of us has as an answer for their concerns and allows us to actually speak.”

Nodding to the perceived stakes, Rep. Cedric L. Richmond (D-La.), a co-chair of Biden’s campaign, accused Trump of trying to start a race war.

“My reaction is, he’s sick. You know, he does this over and over again. He will play the race card, because he’s a racist,” Richmond said Wednesday morning on CNN. “But he plays the race card when he’s stumped, and he’d rather people call him a racist than incompetent.”

Inside the Democratic Party, there are lingering anxieties about whether Biden is effectively responding to the onslaught from Trump. Privately, some party strategists and officials said Wednesday that Biden at times was shaky at the debate and struggled to get his points across. But they said Trump’s belligerence was the main takeaway from the chaotic 90-minute exchange.

Ed Rendell, the former Pennsylvania governor and a Biden ally, said he wished Biden had a crisper answer on law-and-order questions, and would put an emphasis on saying that those engaged in looting and rioting at protests should be prosecuted. He also wished Biden would have reiterated his past opposition to expanding the Supreme Court.

“I would have liked those answers to be a little sharper, but his comments by and large were good,” Rendell said. “Trump has done such a good job in lowering the bar for Biden that literally by standing on his feet for an hour and 45 minutes and giving cogent answers, he really won the debate.”

Rep. Tim Ryan (D-Ohio), a Biden ally, said Biden “was calm and mature and kept it together in the midst of Trump doing everything he can to take an ax to one of the great rituals of our democracy. . . . Trump is just outrageous. It’s like trying to debate a drunk gorilla that’s just going crazy.”

Biden’s campaign said it raised $3.8 million between 10 p.m. and 11 p.m. on Tuesday, breaking its single-hour online fundraising record. It also quickly added a new black T-shirt to its online store, featuring an image of Trump and one of Biden’s stinging questions during the debate: “Will you shut up, man?”

Biden campaign advisers said repeatedly in the aftermath of the first debate that he would attend the next two debates, tamping down speculation stoked by past comments made by House Speaker Nancy Pelosi (D-Calif.) and others that he should not engage with Trump. But Biden’s advisers expressed frustration with how parts of the debate were conducted, and they have expressed those views with the Commission on Presidential Debates about potential changes to the rules and format before the Oct. 15 debate in Miami.

The commission on Wednesday afternoon announced it was reviewing potential changes.

“The Commission on Presidential Debates sponsors televised debates for the benefit of the American electorate,” it wrote in a statement. “Last night’s debate made clear that additional structure should be added to the format of the remaining debates to ensure a more orderly discussion of the issues.”

“We’re 33 years old, and that was the 31st debate. This is the first time we’ve faced anything that existed like last night,” said co-chair Frank J. Fahrenkopf Jr. “We’re working hard to try and come up with something.”

He declined to say what the commission would do.

The second debate in Miami is scheduled to be conducted in a town-hall format, and Biden’s campaign views that as a strength of his, offering the ability to showcase his empathy and compassion, while also potentially presenting challenges for Trump.

Moving ahead, leading Republicans and Trump advisers are expected to encourage the president to let Biden talk more in future debates, hoping the former vice president will make a mistake or take unpopular policy positions, according to several officials and lawmakers involved in the discussions.

“Joe Biden’s greatest liability is his own mind and his own mouth. Tuesday night he didn’t have to use either,” said Josh Holmes, a Republican adviser to Senate Majority Leader Mitch McConnell (R-Ky.).

Josh Dawsey, Felicia Sonmez and Seung Min Kim contributed to this report.