Republican nominee Donald Trump will take the debate stage Sunday night facing not only his opponent Hillary Clinton, but questions about the viability of his campaign.

In the two days since revelations of shocking, vulgar statements captured in a 2005 video, some prominent members of his own party have called on him to quit the race — a request he has flatly rejected. U.S. Sen. John McCain, R-Ariz., the 2008 GOP nominee for president, late Saturday, joined a handful of national Republicans in withdrawing his support from Trump.

Trump’s own running mate, Indiana Gov. Mike Pence, called Trump’s statements “offensive,” but said he was grateful Trump “expressed remorse and apologized to the American people.”

In Georgia, top Republicans slammed his comments about women but none have said they would pull their endorsement for the New York businessman.

How all of this will play out in front of millions of Americans watching the debate, is anyone’s guess. But it’s clear this will be an unprecedented moment in American politics and a critical moment for Trump’s floundering campaign.

“He has to do more than shine,” Randy Evans of Georgia, a member of the Republican National Committee said. “He has to demonstrate to Americans that he’s not the person that’s in the audio recording.”

Matt Borges, chairman of the Republican Party in Ohio, a state that Trump desperately needs to win, said Sunday could be Trump’s last chance.

“Tomorrow’s debate performance is everything,” Borges told The New York Times. “If there’s a chance to recover, that’s it.

For many, however, it’s already too late.

U.S. Rep. Mia Love, R-Utah, a rising star in the party who had yet to endorse Trump, said Saturday she “cannot vote for him.”

“For the good of the party, and the country, he should step aside,” Love said on Facebook.

Trump, for his part, spent much of Saturday inside Trump Tower in New York, meeting with advisers and his family and giving a few interviews. In a video statement released shortly after midnight Saturday, Trump apologized. He later told The Washington Post and The Wall Street Journal that there is "zero chance I'll quit" and that "I never, ever give up."

Instead, Trump vowed to pivot and attack Hillary Clinton and her husband, former President Bill Clinton, over the latter’s record of philandering and Hillary Clinton’s record of defending him.

Clinton, too, is likely to face other uncomfortable questions at Sunday's debate here at Washington University. Wikileaks, the internet-based advocates of transparency, released a trove of new emails Friday that showed Clinton chummy with Wall Street and advocating for "open borders" in the hemisphere.

But, the issues surrounding Clinton's emails were dwarfed by the Trump situation, which was revealed Friday by the Washington Post in a story that immediately threw an already tumultuous campaign into a spiral. In the video accompanying the Post's story, Trump can be heard making vulgar remarks about women as he details how he attempted to forcefully persuade a married woman to have sex with him. Trump brags of groping women's genitals, saying that "when you're a star, they let you do it."

Back in Georgia, state Republican officials continued to blast the former reality television star, but not had yet pulled their endorsement or called on him to step down. Former U.S. Rep. Jack Kingston, R-Savannah, who has served as a Trump adviser defended the nominee on MSNBC.

“If this conversation had happened yesterday or, you know, a year ago, it would be one thing,” said Kingston. “But 10 years ago, in the context of Hollywood – it doesn’t make it right, not at all – but in the same hand, putting it in context, 10 years ago, in a private conversation. It’s a little different than a public policy statement.”

U.S. Sen. David Perdue, R-Sea Island, has also been one of Trump’s top supporters in the state. A spokeswoman Saturday called Trump’s comments “disrespectful,” but Perdue has otherwise not addressed the situation. Both Perdue and Kingston attended the first presidential debate in September to support Trump.

U.S. Sen. Johnny Isakson, facing pressure from Democrat Jim Barksdale to disavow Trump, said the comments were "wholly inappropriate and unacceptable."

“As a husband, father of a daughter and grandfather to five granddaughters, I am disgusted by Trump’s comments,” he added.

Next door in Alabama, however, several Republican elected officials cut ties with Trump.

U.S. Rep. Bradley Byrne, R-Ala., called Trump’s comments “disgraceful and appalling.”

“It is now clear Donald Trump is not fit to be president of the United States and cannot defeat Hillary Clinton,” Byrne said in a statement. “I believe he should step aside and allow Governor Pence to lead the Republican ticket.”

His Republican colleague, U.S. Rep. Martha Roby, also of Alabama, said Trump’s behavior is “unacceptable.”

“I won’t vote for him,” Roby said on Twitter.

WSB Radio host Erick Erickson, long one of the right’s top critics of Trump, said those who helped give Trump the nomination now own the outcome of the election.

"Remember, when Hillary gets sworn in next year, many people told you well before Trump was the nominee that his nomination would cause that," Erickson said on Twitter.