Supreme Court nominee Brett M. Kavanaugh and the woman who has accused him of sexually assaulting her decades ago will testify publicly before the Senate on Monday, setting up a potentially dramatic and politically perilous hearing that could determine the fate of his nomination.

Republicans, including President Trump and Senate Majority Leader Mitch McConnell (Ky.), remained defiant as they scrambled to protect Kavanaugh’s nomination in the wake of the allegation by Christine Blasey Ford, who told The Washington Post in an interview published Sunday that Kavanaugh drunkenly pinned her to a bed on her back, groped her and put his hand over her mouth at a house party in the early 1980s.

But by the end of the day, Senate Republicans had effectively delayed a committee vote planned for Thursday and abandoned tentative plans for the matter to be handled behind closed doors amid growing calls by members of both parties for Kavanaugh and Ford to testify publicly under oath, injecting uncertainty into the nomination.

The White House said in a statement that Kavanaugh “looks forward to a hearing where he can clear his name of this false allegation.”

The hearing sets up a public spectacle that Senate Republican leaders had been hoping to avoid 50 days before midterm elections in which their majority in both chambers is at risk and female voters are energized about casting ballots.

Senate Judiciary Committee Chairman Charles E. Grassley (R-Iowa) said that his staff had contacted Ford to hear her account and held a follow-up call with Kavanaugh on Monday afternoon but that Democrats had declined to participate.

“However, to provide ample transparency, we will hold a public hearing Monday to give these recent allegations a full airing,” he said.

Ford is “willing to do whatever it takes to get her story forth,” her attorney, Debra Katz, said in an appearance on NBC’s “Today” show.

Sen. Susan Collins (R-Maine), a crucial swing vote, indicated that if it emerged that Kavanaugh had been untruthful about the incident, he would not be fit to serve on the court.

“Obviously, if Judge Kavanaugh has lied about what happened, that would be disqualifying,” Collins said, adding that “having the opportunity to observe her being questioned, read a transcript and a deposition and make that kind of assessment is so important.”

Katz on Monday characterized Kavanaugh’s actions as “attempted rape,” adding that Ford feels “that if it were not for the severe intoxication of Brett Kavanaugh, she would have been raped.”

Kavanaugh on Monday issued a fresh denial of the allegations, which have roiled his confirmation process.

“I have never done anything like what the accuser describes — to her or to anyone,” he said in a statement. “Because this never happened, I had no idea who was making this accusation until she identified herself yesterday.”

Yet his denials only prompted further questions. Sen. Orrin G. Hatch (R-Utah), a member of the Judiciary Committee, said that Kavanaugh had told him that he was not present at the party in question — which prompted some to wonder how Kavanaugh could make such a claim given that Ford had never specified the exact date or location of the gathering.

Trump broke his silence on the allegations Monday, praising Kavanaugh as “one of the finest people that anybody has known” and signaling that he supports a hearing on the allegations.

“If it takes a little delay, it’ll take a little delay,” Trump told reporters at an event on workforce development. “It will, I’m sure, work out very well.”

Sen. Lindsey O. Graham (R-S.C.) said he had spoken to Trump twice about the nomination. “The human stuff has really hit home,” Graham said. “You’ve got his wife. His daughter. You’ve gotta listen to people. He’s actually been really good on this in terms of the human element of it.”

Soon after Grassley announced the hearing, Democrats began to protest his decision, insisting instead that the FBI reopen his background check investigation rather than going ahead with a full-fledged public airing of the accusation.

“If there’s a hearing before that investigation, the committee is going to be shooting in the dark with questions,” said Sen. Richard Blumenthal (D-Conn.), a member of the committee. “As a former prosecutor and state attorney general, there’s no way I would put a crime survivor on the stand in front of a jury, let alone the American people, without a full investigation so that I know what the facts are before I start asking questions.”

In a statement Monday, the Justice Department signaled that the FBI doesn’t plan on re-opening Kavanaugh’s background check for now — noting that it forwarded information about Ford’s allegation to the White House, consistent with federal guidelines.

“The FBI’s role in such matters is to provide information for the use of the decision-makers,” a DOJ spokesman said.

It’s unclear whether the committee will call more witnesses to testify Monday in addition to Ford and Kavanaugh. One focus has been on Mark Judge, Kavanaugh’s friend, who Ford said was present at the time of the alleged assault.

“I don’t know what the witness list is going to look like” aside from Kavanaugh and Ford, Senate Majority Whip John Cornyn (R-Tex.), a member of the committee, said Monday evening when asked whether Judge would be called to appear.

As news of the allegations rippled across Washington, supporters of Kavanaugh and Ford rallied to their defense.

Former high school classmates of Ford drafted an open letter applauding her for coming forward with her story and affirming that her experience “is all too consistent with stories we heard and lived.”

Two former girlfriends of Kavanaugh, meanwhile, issued statements defending him as “respectful” and a “perfect gentleman.”

The Judicial Crisis Network, a conservative group that has been a major proponent of Republican nominees to the high court, announced that it would launch a $1.5 million advertising blitz to support Kavanaugh, featuring a longtime friend of the federal judge who would speak to his character.

On Capitol Hill, the debate over the allegations spilled over onto the Senate floor as leaders of both parties made uncharacteristically impassioned remarks.

“Republicans and their staff cannot impartially investigate these allegations. They’ve already said that they are not true,” Senate Minority Leader Charles E. Schumer (D-N.Y.) said.

“The double standard — the twisting of this body into a cruel, nasty partisanship, unprecedented in a feverish desire to fill the bench with people that the other side agrees with — it’s one of the lowest points I have seen in my years here,” he added.

His remarks came shortly after McConnell took to the floor to blast Democrats for not raising Ford’s accusation earlier in the process.

“But now — now, at the 11th hour, with committee votes on schedule after Democrats have spent weeks and weeks searching for any possible reason that the nomination should be delayed — now, now, they choose to introduce this allegation,” McConnell said.

McConnell later told reporters that the Judiciary Committee had “made a good decision” and that “we’re going to go forward with it.”

Underscoring the uncertainty Kavanaugh faces, four senators who are considered swing votes on the nomination issued statements Monday calling for a thorough review of the allegations by Ford, a professor in California.

In addition to Collins, three red-state Democrats — Sens. Joe Donnelly (Ind.), Heidi Heitkamp (N.D.) and Joe Manchin III (W.Va.) — also called for hearings.

The Post left messages Monday with dozens of women who signed on to a letter last week supporting Kavanaugh. Three declined to comment, directly or through family members, and four said the allegation does not change their endorsement. None who spoke with The Post withdrew her support.

“Brett is a good man, a decent man, who respects women,” said Maura Lindsay, who said she knew Kavanaugh while she was a student at Immaculata Preparatory School in the District in the early 1980s. Lindsay emphasized that she stood by the letter.

Lindsay said she received a text from a friend Thursday asking if she would sign a letter attesting to Kavanaugh’s character. She and others said they did not know an allegation of sexual misconduct was about to break in the media.

The women said they did not recognize descriptions of Kavanaugh as a heavy drinker at high school parties.

“He was more likely to corner you and talk to you about some interesting philosophical principle than to try to make out with you,” said one woman, who requested anonymity because she worried the media firestorm would affect her family.

“He was the sweet, thoughtful kind of guy, almost sweetly naive,” the woman said. “I don’t remember him being drunk or being someone who drank a lot, and I cannot say that about some of the other guys.”

Lindsay said Kavanaugh “stood out as the guy on the fringe who was totally in control” at social gatherings. “He was not one of the crazy ones,” she said.

The woman who spoke on the condition of anonymity said it would be wrong to conclude that women who have not returned reporters’ phone calls no longer support Kavanaugh. She and others who spoke with The Post said they were not aware of anyone who had changed their mind as a result of Ford’s allegation.

“People are really angry that our resistance to talking to the media is being portrayed as a lack of support for Brett,” the woman said.

Monica Mastal, who knew Kavanaugh while attending Georgetown Visitation Preparatory School, said she continues to “wholeheartedly” support his nomination.

“When he says that he didn’t do this, I have 100 percent confidence that he didn’t do this,” she said. “I fully stand by the letter.”

Gabriel Pogrund, Elise Viebeck, Matt Zapotosky, Mike DeBonis and Robert Costa contributed to this report.