=Continued=

Jennifer Palmieri, Mrs. Clinton’s communications director, expressed little sympathy for Republicans now fleeing Mr. Trump.

“There was a time when they could have spoken out against him,” Ms. Palmieri said of party leaders like Mr. Ryan. “That time was this summer. Obviously, it is too late now.”

The consequences for both men are enormous. Mr. Ryan and other Republican leaders fear that Mr. Trump’s flagging campaign will imperil their majorities in the House and Senate, and Mr. Trump can ill afford more prominent rejections when he is trying to rally reluctant Republican voters behind him.

Mr. Trump’s candidacy was already in dire condition before Mr. Ryan’s announcement. A poll published Monday by NBC News and The Wall Street Journal found him trailing Mrs. Clinton by a wide margin, drawing less than 40 percent of the vote. The survey was taken before the debate.

And in a sign of how deep divisions now run among Republicans, the chairman of the Republican National Committee, Reince Priebus, held a conference call of his own after Mr. Ryan’s to emphasize his commitment to Mr. Trump. Mr. Priebus told members that the committee was working in “full coordination” with the Trump campaign and planned to direct “a lot” of money to the presidential race.

“Nothing has changed in our support for our nominee,” he said, vowing “an incredible four weeks” until the election.

Mr. Priebus, long a close political ally of Mr. Ryan, made no direct reference to the speaker’s announcement, or to the dozens of governors and members of Congress who have rescinded their support for Mr. Trump.

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Hillary Clinton was buoyant in Detroit. Her campaign released new ads aimed at Republicans. Credit Doug Mills/The New York Times

Representative Scott Rigell of Virginia, a Republican who has long opposed Mr. Trump, said there was a general sense in the House that more humiliating disclosures about Mr. Trump were likely to come before Nov. 8, Election Day.

“There’s a consensus, even among supporters, that the likelihood of something else breaking in a very embarrassing and negative fashion is certainly better than 50-50,” said Mr. Rigell, who joined the call on Monday. “The conference, members, et cetera, are bracing themselves for another salvo of this.”

Mr. Trump seemed to acknowledge that possibility in Pennsylvania, commenting offhand in his speech that if more recordings were to emerge, he would respond with more personal attacks on Mrs. Clinton and her husband.

Mr. Trump’s allies had hoped that the debate would halt the exodus of fellow Republicans from his candidacy, and they publicly implored members of the party on Monday to stick with him through Election Day. Gov. Mike Pence of Indiana, Mr. Trump’s running mate, punctured speculation that he might withdraw from the race by pronouncing himself “proud to stand with Donald Trump” in a visit to North Carolina.

Kellyanne Conway, Mr. Trump’s campaign manager, also offered an ominous warning for Republicans fleeing Mr. Trump. She noted on television that Mr. Ryan had been booed by Trump fans over the weekend in Wisconsin and said she knew of Republican lawmakers who had behaved inappropriately toward young women, and whose criticism of Mr. Trump was therefore hypocritical.

Just as telling as the frustration from outspoken conservatives in the House on Monday was the silence from so many mainstream Republicans in the chamber, who showed little appetite to argue for or with their embattled nominee.

Few anti-Trump voices weighed in on the call with Mr. Ryan. Representative Martha Roby of Alabama, who defected from Mr. Trump on Saturday, said she would contribute significant money to help Republicans hold their House majority. But she also said she would speak with colleagues in private about her decision to withdraw her endorsement in the presidential race.

Representative Charlie Dent of Pennsylvania, a vocal critic of Mr. Trump, asked his colleagues if they were truly confident that there would be no more damaging disclosures. In any case, Mr. Dent argued that the race was effectively over for Mr. Trump.

=To Be Continued=

=Continued=

No new prominent Republicans have withdrawn their endorsements since the debate, but there was a palpable fear throughout the party that Mr. Trump had been damaged beyond repair.

Representative Greg Walden of Oregon, chairman of the National Republican Congressional Committee, urged members on the conference call to take polls in their districts to gauge the effect of Mr. Trump’s political slide.

Mr. Walden said they should brace for a significant erosion of support for Mr. Trump and acknowledged that the shift could hurt congressional candidates, too. He asked the entire caucus to contribute quickly to the party’s campaign arm, making it clear that they needed to strengthen their defenses across the country.

At a briefing for Washington lobbyists later in the day, Mr. Walden acknowledged to donors that Republicans were in uncharted territory and wholly uncertain of what would happen next.

Still, many members were pointed in expressing their dismay to Mr. Ryan, warning him of grave consequences, in November and beyond, if Mr. Trump’s campaign collapses altogether.

Representative Billy Long of Missouri spoke up in Mr. Trump’s defense, citing the danger of losing the Supreme Court if Mrs. Clinton wins.

“Many of us commented that if Hillary picks the next two to four judges, it will change the fabric of our country of 40, 50 years,” Mr. Long said later. “Abortion and the Second Amendment, also, and lots of Supreme Court concerns.”

 =End=