The fusillade from Senate Republicans started Monday morning in Louisville, where Majority Leader Mitch McConnell (Ky.) called on Moore to end his run.
"I believe the women, yes," he said of the allegations leveled against Moore.
Later, National Republican Senatorial Committee Chairman Cory Gardner (R-Colo.) issued a written statement going further. "If he refuses to withdraw and wins, the Senate should vote to expel him," Gardner said. He told reporters afterward that Moore "doesn't belong in the United States Senate."
In a sign of Moore's fading support among conservatives, Sen. Ted Cruz (R-Tex.) pulled his endorsement of his candidacy.
"I am not able to urge the people of Alabama to support his candidacy so long as these allegations remain un-refuted," he told reporters late Tuesday.
The public comments from top Republican senators marked a dramatic escalation from their initial reactions to Thursday's Washington Post report detailing allegations that Moore initiated a sexual encounter with a 14-year-old girl when he was 32.
The intensifying effort against Moore reflected a growing sense that his candidacy is becoming a national emergency for the Republican Party, which is already deeply concerned about its standing with voters ahead of the 2018 midterm elections. In campaigns far from Alabama, Democrats on Monday sought to tie GOP candidates to Moore to take advantage of the controversy surrounding the former judge.
Still, national Republican leaders and their allies were left without a clear path forward, with no way to remove Moore's name from the ballot for the Dec. 12 special election. One last-ditch possibility that some GOP officials were pushing was a write-in campaign by Attorney General Jeff Sessions, who vacated the seat to join the Trump administration.
While top Republicans favor Sessions because they think he would be a widely known and well-liked GOP alternative, unlike other potential contenders, there was considerable skepticism in Sessions's orbit that he would agree to that idea and leave his current post for his old job.
Others floated the prospect of a write-in effort for Sen. Luther Strange (R-Ala.), whom Moore defeated in the primary in September.
Sen. Richard C. Shelby (Ala.) was among the Republicans voicing confidence that Sessions was the party's best hope as a write-in candidate. He told reporters that the attorney general would be a "strong one."
President Trump has been relatively quiet on the controversy while traveling in Asia, adding a degree of uncertainty to how the party should proceed with Moore. Last week, White House press secretary Sarah Huckabee Sanders said Trump believed that if the allegations against Moore are true, he "will do the right thing and step aside."
In recent days, senior Trump administration officials have been in touch with Alabama Gov. Kay Ivey (R) and her inner circle, according to several people briefed on the talks. One person described those conversations as "information gathering" so the White House would know where Ivey stands and to keep the channels of communication open.
But since Trump won't return from Asia until late Tuesday and is still considering his own options regarding how to further address Moore's candidacy, White House officials have been reluctant to lean on Ivey in any way, the people said.
"It's tough having him out of town because no one wants to get too far ahead of him," said one Republican involved in the talks, speaking on the condition of anonymity to describe private deliberations.
McConnell has spoken to Trump about Moore since the allegations were first reported last week, Republicans familiar with their conversations said. Some top Republicans believe that Trump's positioning — wherever he decides to come down — will be crucial in the attempt to force Moore out.
Gardner's call to expel Moore if he is elected was Senate Republican leaders' most aggressive move yet to get the former judge to drop out of the race. But expelling a senator is extremely rare and would require the approval of two-thirds of the chamber to be successful. An actual vote hasn't happened since 1862.
Moore was defiant amid the increasing pressure from party leaders. He wrote on social media that McConnell is the one "who should step aside" and that he has "failed conservatives."
The war of words unfolded on the same day that Beverly Young Nelson, who turns 56 Tuesday, accused Moore, now 70, of sexually assaulting her and bruising her neck in the late 1970s when she was 16 years old.
Nelson said at a news conference at a New York hotel that Moore, then the district attorney of Etowah County, was a regular at a restaurant, Old Hickory House in the northeastern Alabama town of Gadsden, where she was a waitress, and that he would sometimes compliment her looks or touch her long, red hair. She showed a copy of her high school yearbook that she said Moore signed on Dec. 22, 1977, with the inscription: "To a sweeter more beautiful girl I could not say 'Merry Christmas.' "
On a cold night about a week or two after that, Nelson alleges, Moore offered to give her a ride home from work after her shift ended at 10 p.m. Instead of taking her home, Nelson said, Moore pulled the two-door car into a dark and deserted area between a Dumpster and the back of the restaurant.
When she asked what he was doing, Nelson alleges, Moore put his hands on her breasts and began groping her. When she tried to open the car door and leave, Nelson said, he reached over and locked the door. When she yelled at him to stop and tried to fight him off, she alleges, he tightly squeezed the back of her neck and tried to force her head toward his lap. He also tried to pull her shirt off, she said.
Moore denied this latest accusation during a brief campaign appearance Monday evening in Etowah County, where he still lives.
"I can tell you without hesitation this is absolutely false," Moore said, according to the Anniston Star newspaper. "I never did what she said I did. I don't even know the woman. I don't know anything about her. I don't even know where the restaurant is or was."
The new allegation followed an extensive report published Thursday by The Post in which Leigh Corfman alleged that Moore initiated a sexual encounter with her when she was 14 and he was a 32-year-old assistant district attorney. Moore has denied the accusation.
In addition to Corfman, three other women interviewed by The Post in recent weeks said Moore pursued them when they were between the ages of 16 and 18 and he was in his early 30s, episodes they said they found flattering at the time, but troubling as they got older. None of the three women said Moore forced them into any sort of relationship or sexual contact.
Neither Corfman nor any of the other women sought out The Post. While reporting a story in Alabama about supporters of Moore's Senate campaign, a Post reporter heard that Moore allegedly had sought relationships with teenage girls. Over the following three weeks, two Post reporters contacted and interviewed the four women.
Last week, McConnell and many other senators said that "if" those allegations were true, Moore would need to step aside, stopping short of the position he took Monday.
Scott Jennings, a former McConnell aide, wrote a column published Monday endorsing the idea of trying to recruit Sessions to run.
"President Trump should intervene," Jennings wrote in the Louisville Courier-Journal, by demanding that the Alabama Republican Party "withdraw Moore's name as a candidate, which it almost certainly would do if ordered by the White House; dispatch a still-popular Sessions to run a write-in candidacy; and campaign for and hope Sessions wins."
A Sessions spokeswoman at the Justice Department did not immediately comment on the proposal. A Republican close to Sessions, speaking candidly on the condition of anonymity, said that Sessions "has told folks in Alabama that he is not considering it."
Sessions is scheduled to be on Capitol Hill on Tuesday to testify before the House Judiciary Committee.
Inside the White House, Sessions has been floated as a potential replacement, according to two White House officials and several Senate Republican aides.
Sessions — whose once-close relationship with Trump has frayed over the past year following Sessions's recusal from the federal probe into Russian interference in the 2016 election — has dismissed the notion in private but would "of course" listen to the president, should he reach out, according to one White House official.
Sen. Orrin G. Hatch (R-Utah), who expressed solidarity with McConnell's rejection of Moore, wrote on Twitter that Strange would be "an excellent alternative."
At one point Monday, Strange declined to comment when asked if he would mount a write-in campaign or if he had spoken to Moore.
A spokeswoman for the Alabama Republican Party did not immediately respond to a request for comment on the prospect of a write-in campaign. In an interview Sunday with the website Alabama Political Reporter, state GOP Chairman Terry Lathan said "it would be a serious error" for party officials to publicly endorse a write-in candidate.
While Moore's name must remain on the ballot, the state Republican Party has the power to disqualify him — meaning votes cast for him would not be certified.
Senate Minority Leader Charles E. Schumer (D-N.Y.) criticized Moore on Monday. He also distanced himself from the campaign of Democratic nominee Doug Jones, who is trying to demonstrate independence from national party figures in hopes of winning some crossover votes in Alabama, which leans heavily conservative.
"I thought Moore never belonged in the Senate, even before these allegations," Schumer said. As for the Jones effort, Schumer said: "When they ask us for help, we'll do it. But it's been an Alabama race."
As Republican senators returned to Washington on Monday, several made clear to the leadership in phone calls and through colleagues that they would support a tougher line on Moore in the coming days and would encourage Trump to join them once he returns from Asia, according to two people familiar with the discussions.
Asked if there was any easy solution to the Moore situation, Sen. John McCain (R-Ariz.) replied: "No." Then he reconsidered.
"There's one solution," McCain said. "He should never be a United States senator."
Paul Kane, Ed O'Keefe and Elise Viebeck contributed to this report.