The once sacred tradition of a presidential debate -- where candidates typically trade barbs over their vision of the country's future -- exploded into something quite chilling.
The Republican nominee seemingly dismissed the significance of the vulgar language he used toward women a decade ago, apologizing for his conduct but repeatedly saying his remarks were just "locker room talk."
With Hillary Clinton's husband and daughter watching from the audience, Donald Trump lashed into Bill Clinton's infidelities, calling him "abusive." Trump said he would appoint a special prosecutor as president to investigate her -- and even threatened that she would be jailed under his administration.
Clinton didn't take the bait. She repeated first lady Michelle Obama's philosophy articulated at the Democratic convention: "When they go low, we go high."
Trump went into the debate badly needing to recover from one of the worst weekends a major party nominee has experienced in modern presidential history. His performance -- seizing on Clinton's vulnerabilities related to her private email server and record as secretary of state -- could at least stop the panic that has consumed the GOP over the past 48 hours. But it's less clear whether his stern demeanor and prowling stage presence will expand his base of support beyond his most loyal backers, which won't likely be enough to win next month's election.
Clinton made clear that her trouble with Trump goes beyond the partisan clash typical of a presidential campaign. She said she spent much of the past 48 hours thinking about the video that shows Trump making lewd and sexually aggressive remarks about women. She said that she had differed before with Republicans over policy.
"I never questioned their fitness to serve," she said. "Donald Trump is different."
In another unusual twist, Trump slapped down his own running mate, Mike Pence, when the conversation turned to foreign policy. At last week's vice presidential debate, Pence said the US should be prepared to strike Syrian government targets to alleviate the siege of Aleppo.
"He and I haven't spoken and I disagree," Trump said.
That remark could further strain the relationship between Trump and Pence, which was severely tested over the weekend in the aftermath of Trump's comments on women coming to light.
Pacing the stage
Trump paced the stage for much of the debate, which was moderated by CNN's Anderson Cooper and ABC's Martha Raddatz. He frequently interrupted Clinton and had trouble standing still while she spoke, sometimes appearing in her camera shot.
He lost his composure at one point after a fierce exchange with Clinton about her emails, accusing the moderators of not addressing the issue even though Raddatz asked a question about it.
"Nice, one on three" Trump said, insinuating that the moderators were biased against him.
Hours earlier, Trump made a surprise appearance with women who have in the past accused Bill Clinton of inappropriate sexual activity. The women later attended the debate as members of the audience.
During the debate, Trump insisted he had not approached women without their consent but said he was "embarrassed" by the tape. He constantly tried to redivert the conversation even when challenged by CNN's Anderson Cooper to his plans to "Make America Great Again," saying he would go hard after ISIS for example.
Clinton said she had been thinking very carefully about the tape.
"Yes, this is who Donald Trump is," Clinton said. "This is who Donald Trump is but the question our country must answer is this is not who we are."
The turmoil in Trump's campaign have tipped the Republican Party into chaos. Dozens of elected Republicans in Washington and state capitals around the country have condemned Trump -- and many have called for him to step aside. His own running mate, Mike Pence, said Saturday he can't defend Trump's comments.
President Barack Obama joined in the condemnation Sunday, saying the comments suggest Trump "doesn't care much about the basic values."
"One of the most disturbing things about this election is just the unbelievable rhetoric coming at the top of the Republican ticket," Obama said at a campaign event in Chicago for US Senate candidate Tammy Duckworth. "I don't need to repeat it. There are children in the room."
Trump went into the debate under intense pressure to deliver a powerful performance that demonstrates regret and remorse for his conduct. Only a top-notch showing will help Trump stem the GOP exodus away from his campaign that kicked into full gear Saturday. The drama unfolding before tens of millions of viewers is be a fresh reminder how the former star of "The Apprentice" has effectively turned American politics in 2016 into one giant reality show revolving around himself and consuming the whole country.
Trump's attempt to rescue his campaign is all the more complicated since the debate will use a town hall format -- a tricky one for novice candidates -- and will take place in front of a group of undecided voters, some of whom could have pointed questions about his behavior.
Trump must address female voters in particular, given that there is no path to the White House for him unless he can improve his standing among college educated suburban women in key swing states like Pennsylvania and Colorado.
His task is made even more daunting given that he botched the first debate nearly two weeks ago, crushing all the momentum he built up in September and sending his campaign into a spiral, from which, it has not recovered.
Though there was some discussion of policy issues, including tax policy, all eyes were on how Trump responded to the crisis enveloping his campaign. His attempt to save his White House hopes with a big television moment has few precedents in modern political history.
Ironically, one parallel might involve Clinton herself. The future first lady appeared on "60 Minutes" with her husband in 1992 and turned in a stunning performance to rescue his Democratic primary campaign and political career after he was assailed by allegations of infidelity.
Forty years earlier, Richard Nixon pulled off the same kind of high wire act on television that faces Trump when he was in danger of being thrown off Dwight Eisenhower's presidential ticket due to a campaign finance scandal. His appearance, which came to be known as the Checkers speech, was good enough for him to be retained as vice presidential nominee and saved his political future.
Trump needs nothing less on Sunday.