WASHINGTON (Reuters) - Paul Ryan, the top Republican in the U.S. Congress, took the extraordinary step on Monday of distancing himself from Donald Trump, stirring a backlash from some lawmakers and deepening a crisis over his party’s struggling presidential nominee.

In a conference call with congressional Republicans, Ryan all but conceded that Democrat Hillary Clinton was likely to win the White House on Nov. 8 and said he would put his full energy into preserving Republican majorities in Congress so as not to give her a “blank check.”

Ryan, the speaker of the House of Representatives, said he would not defend Trump or campaign for him after the uproar over the New York businessman’s sexually aggressive comments that surfaced on Friday.

Ryan’s announcement added to the party’s worst turmoil in decades and reinforced the growing sense of isolation around Trump, who has never previously run for public office.

Clinton has led Trump in most national opinion polls for months and Trump’s poll numbers have begun to drop further since the emergence on Friday of a video from 2005 showing the former reality TV star bragging crudely about groping women and making unwanted sexual advances.

Trump hit back at Ryan, the Republican vice presidential candidate in 2012, who has frequently been critical of him.

“Paul Ryan should spend more time on balancing the budget, jobs and illegal immigration and not waste his time on fighting Republican nominee,” Trump wrote on Twitter.

Ryan, who had expressed disgust over the tape and canceled a campaign event with Trump over the weekend, did not completely cut ties to Trump. The speaker went back on the Republican conference call later to clarify he was not withdrawing his endorsement.

Many Republican members of Congress are concerned that Trump’s chaotic campaign could ruin their chances of holding their majorities in the House of Representatives and Senate in the November election and could inflict long-term damage on the party.

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During a weekend dominated by criticism of Trump over the lewd remarks, a string of members of Congress, governors and other prominent Republicans called on him to drop out of the race.

House Republicans gave Ryan a rough ride on the call, according to some participants.

“There was an undeniable opposition to the speaker’s tepid support of our nominee,” said U.S. Representative Scott DesJarlais, a Trump supporter, in a comment passed on by an aide.

Many other lawmakers, some of whom did not want to be named publicly criticizing the speaker, said members frequently told Ryan on the call to stand by Trump.

Nonetheless, nearly half of all 331 incumbent Republican senators, Congress members and governors have condemned Trump’s remarks, and roughly one in 10 has called on him to drop out of the race, according to a Reuters review of official statements and local news coverage.

Republican National Committee Chairman Reince Priebus used an afternoon conference call with RNC members to emphasize there was no rift with Trump and that the committee, the party’s leadership and fundraising arm, still backed the nominee, two RNC members who spoke on condition of anonymity said.

RNC STILL ON BOARD

“Any suggestion that the RNC isn’t fully supporting the Trump-Pence ticket is wrong,” one RNC member said, describing the message. “We are fully on board. We are going to devote every ounce of effort and resource into helping the Trump-Pence ticket win and all the other candidates up and down the ballot.”

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Any attempt to replace Trump on the ballot this close to Election Day would face huge legal and logistical hurdles.

A defiant Trump went on the offensive in a vicious presidential debate on Sunday, saying Clinton, a former secretary of state would go to jail if he were president and attacking her husband, former President Bill Clinton, for his treatment of women.

The debate, the second of three before the vote, was remarkable for the brutal nature of the exchanges between the two.

Trump stayed on the attack on Monday, describing Bill Clinton as “a predator” and saying: “If they want to release more tapes saying inappropriate things, we’ll continue to talk about Bill and Hillary Clinton doing inappropriate things. There are so many of them.”

“She goes out and says: ‘I love women, I’m going to help women.’ She’s a total hypocrite,” he told supporters in Ambridge, Pennsylvania.

Clinton accused Trump of brushing off criticism of his comments about women.

“On Friday, the whole world heard him talking about the terrible way he treats women. And last night when he was pressed about how he behaves, he just doubled down on his excuse that it’s just locker room banter,” she told a rally at Wayne State University in Detroit.

The television audience for the debate fell sharply from their first, record-breaking encounter in September.

Nielsen data supplied by CNN for 10 broadcast and cable channels on Monday showed that 63.6 million Americans tuned into the 90-minute debate on Sunday, well below the record 84 million that watched the first face-off.

An NBC News/Wall Street Journal opinion poll released on Monday showed Clinton increasing her lead. The survey, conducted after the video release but before the debate, showed Clinton with 46 percent support among likely voters in a four-way matchup including two minor party candidates, compared with 35 percent for Trump.

The Reuters/Ipsos State of the Nation project released on Monday estimated that Clinton had at least a 95 percent chance of winning the 270 Electoral College votes needed to become president. The polling did not capture reaction to Trump’s performance in Sunday’s debate or the release of the Friday videotape.