Updated at 11 a.m. Tuesday with comments from Attorney General Jeff Sessions and House Speaker Paul Ryan.

WASHINGTON — Republicans are scrambling to distance themselves from Alabama Senate nominee Roy Moore after new allegations of sexual advances on underage teens, with some lawmakers threatening to expel him from office if elected.

Texas Sens. Ted Cruz and John Cornyn, among the Republicans who endorsed the candidate, withdrew their support Monday amid the fallout.

On Tuesday, Attorney General Jeff Sessions, whose seat Moore is seeking, said during testimony before the House that he has "no reason to doubt" the women leveling sexual misconduct allegations. He declined to say whether Moore should step aside, citing Justice Department restrictions. But Speaker Paul Ryan was less constrained.

"No. 1, these allegations are credible. No. 2, if he cares about the values and people he claims to care about, then he should step aside," Ryan told reporters.

With one woman already accusing Moore of sexual contact when she was just 14, a second surfaced on Monday alleging aggressive sexual behavior when she was 16 and he was 30, and said he had made advances before she turned 16.

Moore, a crusader for public displays of the Ten Commandments and a hero to some conservatives, has called the allegations a politically motivated "witch hunt." He denied knowing the latest accuser and showed no sign that he might give into pressure and drop his Senate bid.

Earlier in the day, Senate Majority Leader Mitch McConnell called on Moore to step aside, saying, "I believe the women." Hours later, the head of the party's Senate campaign arm said the Senate should expel Moore if he manages to win a Dec. 12 special election -- the most dramatic steps yet as Republicans try to minimize collateral damage from a nominee accused of illegal sexual contact four decades ago.

"He is unfit to serve in the United States Senate," said Sen. Cory Gardner, R-Colo., chairman of the National Republican Senatorial Committee.

A short time later, Cornyn, McConnell's No. 2, withdrew his endorsement but distanced himself from talk of expulsion, exposing a rare public schism among GOP leaders.

"It's premature to talk about expelling someone who hasn't been elected," said Cornyn, a former Texas Supreme Court justice.

He called the allegations "disturbing and, if true, disqualifying." But in a statement withdrawing his endorsement, Cornyn said he would "leave the final judgment in the hands of Alabama voters -- where it has always belonged."

That left the focus on Cruz and Kentucky Sen. Rand Paul, who were among the highest profile GOP conservatives still backing Moore's candidacy.

That changed Monday night when Cruz said he couldn't continue to recommend Moore to voters unless he offers a "strong, persuasive rebuttal" of the allegations.

"There are serious charges of criminal conduct that, if true, not only make him unfit to serve in the Senate, but merit criminal prosecution," Cruz said, adding, "The people of Alabama deserve to have the option of voting for a strong conservative who has not committed criminal conduct."

Whoa. @NRSC chair Gardner says if Moore wins election, Senate should vote to expel him pic.twitter.com/1xfci9y3GK — Alex Roarty (@Alex_Roarty) November 13, 2017

For days, McConnell and other leading Republicans had said that Moore should drop out "if" the allegations proved true. McConnell notably backed Moore's opponent, Sen. Luther Strange, appointed to replace Sessions, in a late September primary runoff. So did President Donald Trump.

Last week, Cornyn and Cruz called the allegations about the former chief justice of the Alabama Supreme Court"troubling" but stood by their endorsements.

GOP Sens. Mike Lee of Utah and Steve Daines of Montana were the first to ditch their support last Friday. Sen. Bill Cassidy of Louisiana followed suit over the weekend.

Arizona Sen. Jeff Flake said on Monday that he would vote for the Democrat over Moore, and would vote to expel him if it comes to that. Indiana Sen. Todd Young, another Republican, called the allegations "far more persuasive than the denials," and he called on Moore to quit the race.

The Senate can't prevent Moore's election but could expel him with a two-thirds vote. Senate records show that 15 senators have been expelled, the last in 1862; all but one was charged with treason for support of the Confederacy. Many others resigned to avoid expulsion, most recently Oregon Sen. Bob Packwood, who faced sexual misconduct allegations in 1995.

Latest allegations

Beverly Young Nelson, at a news conference in New York with attorney Gloria Allred on Monday, said she was 15 when Moore began courting her. Alabama's age of consent for sexual conduct is 16. At the time, Moore was a prosecutor on his way to statewide office on the Supreme Court.

"He wrote in my yearbook as follows: To a sweeter more beautiful girl I could not say Merry Christmas. Christmas 1977. Love, Roy Moore...and he signed it, Roy Moore, DA," Nelson said.

Cruz said that he found that disturbing.

"Grown men don't typically sign high school girls' yearbooks. As the father of two young daughters, that is a disquieting allegation," Cruz said.

Nelson recounted an incident when she was 16 and in high school, and working at a restaurant where Moore was a regular customer. She says he groped her breasts, locked a car door to prevent her from escaping, tried to undress her and pushed her head toward his groin.

Nelson says Moore asked to write in her yearbook. "He wrote in my yearbook as follows: To a sweeter more beautiful girl I could not say Merry Christmas. Christmas 1977. Love, Roy Moore...and he signed it, Roy Moore, DA." — Daniel Dale (@ddale8) November 13, 2017

On Monday, Moore called her allegations "absolutely false."

"I never did what she said I did. I don't even know the woman. I don't know anything about her," Moore told reporters at a news conference, his wife by his side.

Nelson's story followed an explosive report published in The Washington Post last week in which four women said Moore pursued them sexually when they were teens and he was in his 30s.

Leigh Corfman said she was just 14 when Moore, then 32, initiated sexual contact with her in 1979.

Residents of Gadsden, his hometown, have reportedly said he routinely "flirted" with teenage girls at the local mall, though he was years older.

Moore has also denied those allegations and threatened to sue the newspaper. In a statement last week, Moore called the claims "completely false" and a "desperate political attack by the National Democrat Party and The Washington Post" on his campaign.

Moore has not, however, disputed pursuing teenage girls when he was in his 30s. When Fox News host Sean Hannity asked him Friday night if that was his common practice, he replied: "Not generally, no."

Support slipping

Two polls released since the allegations were published show Moore's support slipping. One survey released on Sunday shows Democrat Doug Jones, a former federal prosecutor, in the lead for the first time.

Republicans hold a two-seat majority in the Senate, so the loss of the Alabama seat would imperil tax overhaul plans and much of their agenda in coming months. But they also faced the prospect of being tarnished by the election of an accused child molester in their ranks.

McConnell and others were exploring a write-in option in a bid to keep the seat in GOP hands, with some floating that Sessions could leave the Justice Department to return to the Senate.

Over the weekend, the White House exerted no political pressure for Moore to drop out, and top Trump aides continued to play for time on Sunday news shows.

"If more evidence comes out that can prove that he did this, then sure, by all means he should be disqualified. But that's a huge if, and I think we have to allow that more facts come out," White House legislative affairs director Marc Short said Sunday on Meet the Press. "There's no Senate seat more important than the notion of child pedophilia.... But having said that, he has not been proven guilty."

Feeling the heat

Last week, Democrats blasted both Texas senators for standing by Moore despite the serious on-the-record allegations against him, many from women who call themselves loyal Republicans.

It’s almost as if it doesn’t bother him 🤔 https://t.co/Oy4QpNLDi2 — Beto For President (@BetoPres2020) November 13, 2017

"It's almost as if it doesn't bother him," Rep. Beto O'Rourke, an El Paso Democrat hoping to unseat Cruz next year, tweeted on Monday. Three days earlier he chided Cruz in a fundraising email for supporting the election of "a man who preyed on young girls to the U.S. Senate."

Cruz's condemnation of Moore is particularly notable as it could put him sideways with the Senate candidate's top backer, Breitbart News executive chairman Steve Bannon.

After leaving his post as Trump's chief strategist in August, Bannon pledged to recruit opponents to challenge Republican incumbents in next year's primaries -- except for Cruz.

Bannon has declared a "season of war" on the GOP establishment, leveling much of his criticism at McConnell. Moore himself hit back at McConnell early Monday, asserting that if anyone should quit politics, it should be him.

In the hours before Cruz clawed back his support, his top strategist during his 2016 presidential bid, Jason Johnson, remarked on Twitter that McConnell's frontal assault on Moore "just guaranteed" his election to the Senate.