By Maeve Reston CNN

(CNN) -- After a year of agonizing, Donald Trump's vulgar hot mic comments proved to be the final straw for many top Republican Party leaders.

A day after the release of the lewd tape, House and Senate members rescinded their endorsement of Trump in increasing numbers -- and others were sure to follow. In the hours after The Washington Post published a vulgar video of Trump bragging about his ability to grope women as a benefit of his celebrity, Republicans were quick to condemn Trump, but slow to rescind their endorsement.

That all changed Saturday morning as top Republicans in marquee Senate races, including New Hampshire Sen. Kelly Ayotte and Rep. Joe Heck of Nevada, said they could no longer support Trump.

"I'm a mom and an American first, and I cannot and will not support a candidate for president who brags about degrading and assaulting women," Ayotte said in a statement, adding she would write Pence's name in on her ballot.

"I believe our only option is to formally ask Mr. Trump to step down and allow Republicans the opportunity to elect someone who will provide us with the strong leadership so desperately needed and one that Americans deserve," Heck said, appearing with former GOP nominee Mitt Romney Saturday.

Arizona Sen. John McCain also withdrew his support for Trump. In addition to the vulgar comments that surfaced Friday, McCain also cited Trump's controversial remarks earlier in the week about the "Central Park 5" -- saying he believed they were still guilty in a 1989 rape despite being exonerated years ago -- in making his decision.

"Donald Trump's behavior this week, concluding with the disclosure of his demeaning comments about women and his boasts about sexual assaults, make it impossible to continue to offer even conditional support for his candidacy. Cindy, with her strong background in human rights and respect for women fully agrees with me in this," McCain said.

"Cindy and I will not vote for Donald Trump," he continued. "I have never voted for a Democratic presidential candidate and we will not vote for Hillary Clinton. We will write in the name of some good conservative Republican who is qualified to be president."

Other key figures including Alaska Sen. Dan Sullivan, Missouri Rep. Ann Wagner, former California Gov. Arnold Schwarzenegger and Ohio Gov. John Kasich also called for Trump to step aside.

It was a sea change from Friday night, when only two Utah politicians pulled their support of Trump: Gov. Gary Herbert and House Oversight and Government Reform Committee Chairman Jason Chaffetz.

But other high-profile Republicans, including House Speaker Paul Ryan and Republican National Committee Chairman Reince Priebus, haven't backed away from their endorsements of Trump even as they blasted his comments.

The cascade of strong condemnations of Trump on Saturday however, could accelerate the GOP's move toward a tipping point with Trump. Not only are Democrats trying to pressure GOP to cut ties with their nominee, but some Republicans are exploring whether there is any way to keep Trump from remaining their standard bearer.

Trump has survived so many shocking moments this year that most pundits have stopped predicting his downfall. But many Republican strategists said this weekend that the tape -- with Trump's casual suggestion that he could get away with sexual assault -- could be a death blow to his campaign.

Trump made the first step toward recovery early Saturday by issuing a defiant apology. "I said it, I was wrong and I apologize," Trump said in a video in which he also doubled down on his criticism of Bill and Hillary Clinton.

He insisted in interviews Saturday with The Washington Post and The Wall Street Journal that he wouldn't step down and greeted supporters on the sidewalk outside Trump Tower.

It was in many ways the final chapter of the uncomfortable waltz that Republicans have carried on all year with Trump. In key battleground states, candidates and their advisers have agonized over how to deal with Trump, straining to find language that shows they respect the will of the Republican voters, while trying to shield themselves from the stain of his more controversial comments.

Republican leaders across the spectrum seemed mostly horrified by Trump's breezy descriptions of potentially criminal conduct in his conversation with Billy Bush on "Access Hollywood," which was captured on a hot microphone in 2005 and released by The Washington Post.

'Sickened'

In the most telling sign that the GOP may be on the verge of a break with Trump, Ryan said in a statement that Trump would no longer be attending a Republican unity event with Ryan in Wisconsin Saturday, and that he is "sickened by what I heard today."

"Women are to be championed and revered, not objectified. I hope Mr. Trump treats this situation with the seriousness it deserves and works to demonstrate to the country that he has greater respect for women than this clip suggests," Ryan said in his statement. "In the meantime, he is no longer attending tomorrow's event in Wisconsin."

Ryan reiterated Saturday that Trump's comments were a "troubling situation" but didn't pull back his endorsement.

Still, he's sending a clear signal to the many vulnerable House and Senate Republicans that it is fair game to criticize Trump in harsh terms. Before cutting ties with Trump Saturday, Ayotte was the first vulnerable Republican incumbent to weigh in Friday, calling Trump's comments "totally inappropriate and offensive."

Ohio Republican Sen. Rob Portman, who has pledged to support the GOP nominee, said Trump's comments were "offensive and wrong and he was right to apologize."

Pennsylvania GOP Sen. Pat Toomey called Trump's remarks "outrageous and unacceptable." Nevada Congressman Joe Heck, who is in a close race for Senate, said he condemned Trump's comments "in the strongest possible terms" and that the language he used was "disgraceful." Mark Kirk, an Illinois Republican who has been critical of Trump, called him a "malignant clown -- unprepared and unfit to be president of the United States."

Dems blast GOP

Democrats were quick to charge that Republicans weren't going far enough. Democratic operatives made it clear that their strategy in the days ahead would be to force GOP candidates not just to say whether they condemned the comments, but whether they believed Trump should still be commander-in-chief.

A number of strategists predicted Friday that the emergence of the "Access Hollywood" tape would make it much easier to sever ties with Trump over the coming days.

How the shocking hot mic tape of Donald Trump was exposed

John Weaver, a strategist for Ohio Gov. John Kasich, urged Republicans in a tweet to "Cut Trump loose. If u have endorsed, rescind. U work for campaign, can resign. #Two Paths."

"Condemning Trump's comments while still endorsing, supporting him is outrageous," Weaver later tweeted. "#TwoPaths are available. Choose the right one."

Steve Schmidt, a Republican strategist who advised 2008 presidential candidate John McCain, noted that the Trump campaign has been in a spiral since the last debate.

"At a time when poll numbers are collapsing, this is a comportment and temperament issue. It's devastating," Schmidt said, noting that the new revelations come a week after Trump was "hate tweeting" at a former Miss Universe at 3 am.

"Most every Republican has tried to accommodate the nominee of the party despite things they find deeply awkward. We're moving into a new phase here," Schmidt said.

He noted that Trump has given little indication that he is preparing for the second debate, suggesting a strong possibility of another flubbed performance.

"If the election were held tomorrow, Republicans are down seven Senate seats, so by Monday morning you're going to see Republicans all over saying Hillary Clinton is going to win the election and we need to have divided government to keep a check on her," Schmidt said. "And people will be jumping off the boat like it's the end of the Titanic."

Shock at Trump's comments

Beyond the big names, many Republicans expressed shock at Trump's comments, particularly those who formerly worked for Ted Cruz, and did not appreciate the Texas senator's recent endorsement of Trump.

Cruz strategist Jason Johnson tweeted Friday: "Just another Friday in #2016. Can't even watch the news with my kids."

Cruz also criticized Trump, along with other former Trump primary rivals such as Jeb Bush.

"As the grandfather of two precious girls, I find that no apology can excuse away Donald Trump's reprehensible comments degrading women," Jeb Bush tweeted.

Democrats seek to punish GOP Senate candidates over Trump audio

While Trump had few defenders on Friday, some of his advisers said they believed he could ride out the controversy.

Faith and Freedom Coalition Founder and Chairman Ralph Reed, who sits on Trump's religious advisory board, said that he believed people of faith would pay more attention to where they aligned with Trump on the issues like abortion, Planned Parenthood and the economy.

"I think a 10-year-old tape of a private conversation with at TV talk show host ranks pretty low on their hierarchy of their concerns," Reed said, adding that the tape did not change his opinion of Trump. "Everybody falls short of a standard of perfection, but Donald Trump's been married to Melania for 10,11, 12 years now. And he has a great family and has a tremendous relationship with his children... I think this case is ancient."

CNN's Ashley Killough, Dana Bash, Gloria Borger and Betsy Klein contributed to this report

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