Hours before a televised debate widely expected to define the presidential campaign - and the political career of Donald Trump - the GOP nominee remained defiant even as a growing number of fellow Republicans continued to call on him to exit the race.

The second debate between Trump and Democrat Hillary Clinton will begin at 9 p.m. Eastern time at Washington University in St. Louis.

About an hour and a half before the debate began, Trump hosted a short - and highly unusual - news conference with four women, all of whom said they had been mistreated by the Democratic nominee Hillary Clinton or her husband, former President Bill Clinton. One of the women was Paula Jones, who had accused Bill Clinton of sexual harassment in the early 1990s. Another was Juanita Broaddrick, who at the news conference said Bill Clinton had raped her in 1978.

"Mr. Trump may have said some bad words," Broaddrick said. "But Bill Clinton raped me and Hillary Clinton threatened me. I don't think there's any comparison."

Broaddrick has made such statements before, but it has never been criminally litigated, and the Clintons deny the accusations.

As Trump began and ended the news conference, reporters shouted questions related to a 2005 video that emerged on Friday, in which Trump spoke about kissing and groping women he met. "Mr. Trump does your star power allow you to touch women without their consent?" a reporter asked. Trump ignored the questions, then left.

For Trump, the stakes for this debate would have been high in any event: He had seen his poll numbers begin to slide after a weak and rambling performance during the first debate in late September.

Now, however, Trump is in worse shape - and in far greater need of a surprising, campaign-changing performance. That's due to the release of the 2005, video, first published by The Washington Post. It set off a cascade of criticism from Trump's fellow Republicans - and led dozens of them to formally renounce the party's nominee.

Trump's supporters said they were hoping to see a humble, focused performance, in which he could seem contrite about the 2005 remarks, and then move on.

"He has to reach inside himself and realize what he's capable of doing. He has to live it out, and it's going to be a uniquely personal moment. No one else can figure it out," said former House speaker Newt Gingrich, R-Ga.

On Sunday, however, Trump was showing no sign of a contrite approach. Instead, in interviews and social media posts, Trump made clear that he has no plans to back down - and that he intends to criticize Clinton for her treatment of women who over the years have accused her husband of unwanted sexual advances.

Trump also seemed to blast his fellow Republicans, scorning them for leaving him at this moment.

"So many self-righteous hypocrites. Watch their poll numbers - and elections - go down!" read one Trump tweet Sunday.

"Tremendous support (except for some Republican "leadership"). Thank you," another read.

The video shows Trump bragging in crude terms about kissing and groping women, something he said he has license to do because he is a "star." The remarks were taped in 2005 as part of a segment for the NBC entertainment show "Access Hollywood."

Dozens of elected officials, including Sen. John McCain, R-Ariz., said Saturday that they could no longer support Trump. A growing chorus called for him to drop out of the race. Even his running mate, Indiana Gov. Mike Pence, said he could not defend Trump's remarks. Trump was scheduled to campaign with House Speaker Paul Ryan on Saturday in Wisconsin, but Ryan asked the nominee not to attend. Pence was scheduled as a stand-in, but he, too, decided to stay away. Although Ryan criticized Trump's remarks, he has not withdrawn his support for the candidate.

As Trump jetted to St. Louis, Sen. Jeff Sessions, R-Ala., was on the campus of debate host Washington University on Sunday afternoon with his phone to his ear urging fellow congressional Republicans to settle down and stick with the party's standard-bearer.

"He's charged up," Sessions said of Trump in an interview with The Post. "I believe he can turn this around. I think our party leaders need to slow down and give him a chance to make his case."

He added, "I'm disappointed some people felt the need to respond so quickly."

Sessions also denied a rumor that has circulated among GOP insiders that he had candidly suggested to Trump on Friday that the businessman should consider leaving the race.

"It's not true, and I never came close to saying that," Sessions said. "I came to [Trump Tower] toward the end of the night, and he asked me some questions. He was serious and understood the problems and the significance of it. So we talked. But it was about the significance, and he wasn't in denial that this was some normal little blip that wasn't going to have any impact. He understood it had a life of its own and was already taking off."

Several Clinton advisers and allies said they expect Trump to enter the debate angry, on the defensive and ready to lash out. Clinton will be prepared, but she sees no need to respond point by point, one aide said.

There is a view, however, that Trump could adopt the mindset of a "wounded animal," as one aide put it, which could make him more dangerous and unpredictable.

"The dynamic is he's done and is he going to blow things up and take other people down as he goes? It's what a bully does or what a loser does," said Jim Manley, a former aide to Senate Minority Leader Harry Reid, D-Nev. "You know you're losing, so you might as well inflict a maximum amount of damage. With him, you never know."

Added Clinton communications director Jennifer Palmieri: "We understand that this is uncharted territory to face an opponent that is in the grips of a downward spiral in terms of his own party belatedly walking away from him. So she has a lot of experience, she is very tough, and she'll be prepared to handle whatever comes her way."

Palmieri also sought to measure expectations by predicting that the town hall format could help Trump. En route to St. Louis on Clinton's campaign plane, Palmieri said Trump did well in a forum on national security in terms of tone, and she noted that voter questions could keep him relatively focused.

There are "guardrails that may keep him from spiraling as he did in the first debate," Palmieri said. "For Secretary Clinton, it's a great format when she's able to talk directly to voters about issues that they care about in their lives.

"We think there are a lot of voters who are newly open to hearing from her. And that's what we spent most of our time in prep doing and that's what we see the opportunity is here," she added.

Former New York mayor Rudy Giuliani gave a hint Sunday of how Trump plans to respond, stating that the real estate mogul will probably apologize. Giuliani said Trump is prepared to talk about the issues facing the country. He said that Trump feels badly about the controversy and that the remarks don't reflect who he is.

"I think he made a full and complete apology for it," Giuliani said of the tape on CNN's "State of the Union" on Sunday morning. "He's probably gonna do it again tonight."

But Giuliani also signaled that Trump has not ruled out using former president Bill Clinton's infidelities to attack his opponent. Trump again tweeted Sunday morning about Juanita Broaddrick, whose accusation that the former president had raped her in 1978 was never litigated in criminal court and has been denied by the Clintons.

Robby Mook, Clinton's campaign manager, said on CBS' "Face the Nation" that the Clintons had a "rough time in their marriage 20 years ago" and that voters want to focus on the issues facing the country.

"I think Donald Trump's campaign is spiraling. They are trying to figure out a way to dig out of this mess," Mook said, noting that the race is between Trump and Hillary Clinton, not Bill Clinton. "If we need to discuss issues that were raised in that video with Donald Trump, that's fine, but the question here is what is Hillary Clinton's take on that issue, not her husband's."

Giuliani appeared in place of Republican National Committee Chairman Reince Priebus, who declined to show up for scheduled appearances on the Sunday morning talk shows, as did Trump's campaign manager, Kellyanne Conway, and top surrogate Gov. Chris Christie, R-N.J.

Giuliani had difficulty justifying Trump's words and the defiant apology the nominee issued late Friday, which morphed into an attack on the Clintons.

"You're saying that the words are wrong. How about the actions?" Chuck Todd asked Giuliani on NBC's "Meet the Press."

"Well, the actions would be even worse if they were actions. Talk and action are two different things," Giuliani said.

On ABC's "This Week," he seemed to acknowledge that Trump's comments on the tape suggested sexual assault.

"What Trump is describing in that tape is sexual assault," host George Stephanopoulos said.

"That's what he's talking about," Giuliani said.

Giuliani got into a tense exchange with "State of the Union" host Jake Tapper, who tore into the defense that Trump engaged in "locker room" banter on the tape.

"First of all, I don't know that he did that to anyone. This is talk, and, gosh almighty, he who hasn't sinned cast the first stone here," Giuliani told Tapper.

Tapper responded tersely: "I will gladly tell you, Mr. Mayor, I have never said that, I have never done that. I am happy to throw a stone. I don't know any man - I've been in locker rooms, I've been a member of a fraternity - I have never heard any man, ever, brag about being able to maul women because they get away with it. Never."

Giuliani responded: "The fact is men, at times, talk like that, not all men, but men do. He was wrong for doing that. I'm not justifying it. I believe it's wrong."

After the controversy erupted Friday, Clinton pinned a tweet that contained the Trump video and the words "Women have the power to stop Trump."

President Barack Obama, speaking Sunday at a fundraiser for Rep. Tammy Duckworth, D-Ill., who is seeking to unseat incumbent GOP Sen. Mark Kirk, said he doesn't need to repeat some of the things Trump has said "because there's children in the room."

"Are we really going to risk giving Donald Trump the majority he needs to roll back all the progress we've made over the last eight years?" he asked the crowd.

Obama said Trump has demeaned and degraded women, minorities, immigrants, people of different faiths and the disabled.

"That tells you a couple things. It tells you that he is insecure enough that he pumps himself up by putting other people down. Not a character trait that I would advise for somebody in the Oval Office," Obama said.

More tapes showing Trump making crass remarks about sex and women surfaced on Saturday, including one in which the Republican nominee described his own daughter as "voluptuous."

Clinton campaign chairman John Podesta said on "Fox News Sunday" that Trump's remarks show his true character.

"This is who this guy is," Podesta said. "I hope every voter actually takes the time to see what is really on that tape, and I hope that all of their children don't get to see what's on that tape."

Gingrich, an experienced debater, said he had been in touch with Trump advisers since arriving home from a trip to Italy. While Gingrich was dismissive of the spate of GOP defections and the calls throughout the party for Trump to drop out - "a fantasy" - he acknowledged that the stakes are very high for the nominee. "It's going to be a real war. The other side will hit as hard as they can, and you can't flinch."

Gingrich said Trump "has got to be contrite about his language but far more aggressive about his policy" so that the large national television audience walks away with a firmer-than-ever grasp his economic populism and views on trade.

"He has to reach inside himself and realize what he's capable of doing. He has to live it out, and it's going to be a uniquely personal moment. No one else can figure it out," Gingrich said.

Gingrich urged Trump to go after Hillary Clinton - but not for former president Bill Clinton's past. Gingrich said putting an emphasis on the latter, long a favorite GOP target, was risky: "The only hope for the Trump campaign is to make sure Hillary's leaked speeches to Wall Street are as well known by mid-October as Trump's bad language."

Meanwhile, Clinton's allies tried to tamp down the significance of remarks the Democratic nominee apparently made to Wall Street groups that included her dreams of "open trade and open borders," remarks that were taken from hacked emails and are likely to come up during Sunday's debate.

Although Clinton's surrogates did not deny that she gave the speeches, they said they could not verify the authenticity of the hacked emails, which were made public Friday by WikiLeaks and were apparently lifted from Podesta's account. They also tried to counter critics who said the emails illustrate how Clinton is out of touch with working Americans and bends her positions to suit the audience to which she is speaking.

"Her public position and what she's going to fight for as president are one in the same," Mook said.