ST. LOUIS — It began with two presidential candidates tensely refusing to shake hands at the opening of a nationally televised debate, breaking decades of civil tradition.

By the time it was over, one of them had vowed that, if elected, his opponent would be in jail.

In what was undoubtedly the angriest presidential debate in memory, Donald Trump and Hillary Clinton stood on a St. Louis stage Sunday and presented two vastly different plans for America’s future while savaging each other’s pasts.

Trump, the Republican real estate mogul, was on the hot-seat almost immediately after the start of the 90-minute exchange at Washington University’s Athletic Complex over a 2005 video released 48 hours earlier in which he was caught bragging about his sexual aggression against women.

“He is not fit to be president and commander in chief,” said Clinton, the Democratic former senator and secretary of state, seizing on questions from an audience member and a moderator about the tape. “What we all saw and heard on Friday … represents exactly who he is.”

Trump dismissed the incident as “locker room talk,” and said, “I am not proud of it,” before pivoting to bring up former President Bill Clinton’s episodes of alleged sexual aggression in the past and Trump’s allegation that Hillary Clinton “attacked those same women.”

She also came under fire over her mishandling of official emails while she was secretary of state under questioning from Trump, who turned in a clearly more disciplined performance Sunday than he did in the first debate two weeks earlier.

The most remarkable moment in the debate may have come when Trump, expanding on the email allegations, openly threatened to use the powers of the presidency to go after her should he win the White House.

“If I win, I am going to instruct my attorney general to get a special prosecutor to look into your situation,” Trump said. “We’re going go get a special prosecutor and we’re going to look into it.”

Clinton pointed to the comment to say it’s a “good thing” he’s not in charge of the law.

“Because you’d be in jail,” Trump shot back, sparking applause from his supporters in the room.

The second debate came under what almost couldn’t have been worse circumstances for Trump. His performance in the first debate was widely panned, pressing existing questions about his knowledge and temperament. That was followed by a week’s worth of political injuries, some self-inflicted, including his fat-shaming campaign against a former beauty queen and damaging revelations about his tax returns and his charitable foundation.

Then came Friday’s explosive release of a video from 2005 in which Trump is heard bragging about trying to seduce a married woman, groping and kissing other women against their will and getting away with it because of his fame.

By the time the microphones came on at Washington University on Sunday night, more than two dozen prominent Republican politicians had withdrawn their earlier endorsements of Trump. Many others had issued scathing renunciations of the comments that stopped short of withdrawing support, while making it clear that his debate performance was going to determine if he kept it.

Trump hinted for two days after the release of the tapes that he might play the Bill Clinton card, using the former president’s sexual controversies to counter his own. In fact, he went there even before the debate started.

Less than two hours before the start, Trump held a surprise news conference with Juanita Broaddrick and three other women who claim to have been victimized by either Bill or Hillary Clinton.

“Actions speak louder than words,” said Broaddrick, a nursing home administrator who has long alleged Clinton raped her decades ago. “Mr. Trump may have said some bad words, but Bill Clinton raped me and Hillary Clinton threatened me. I don’t think there’s any comparison.”

Trump spoke little during the event, introducing the women as “courageous” and not taking questions afterward.

At the start of the debate, the two candidates walked onto the stage at the same time from opposite ends of the stage, but did not shake hands, in defiance of long tradition in televised debates, and instead just stood next to each other for the opening applause. The moment – a clear testament to the personal vitriol between the two candidates — created a palpable moment of tension in the debate hall.

Clinton, after attacking Trump over his comments about women, expanded the attack to remind voters that he had previously attacked the family of a fallen U.S. soldier, a federal judge of Mexican descent, a handicapped reporter and others.

“He never apologizes to anyone about anything,” she said. “He never apologized for the racist lie that President Obama was not born in the United States of America.”

Trump responded by repeating a disproven allegation he has made before, that it was actually Clinton who started the “birther” movement, and suggested she’s the one who owes Obama an apology.

Trump repeated several other previously disproven assertions – that he opposed the Iraq War before it started and that the U.S. has one of the highest tax rates in the world, for example – but in general didn’t appear to commit as many clear gaffes as he did during the first debate.

When Trump was asked whether he used an old $916 million reported business loss on leaked tax forms to avoid paying taxes for years afterward, as many have been speculating, his answer was a shrug: “Of course I do … I absolutely used it,” he said, then turned the question to the fact that Clinton, while in the Senate, didn’t eliminate the loophole he used. “Why didn’t she do something about it?”

Asked as the final question whether there was anything positive they could say about  each other, Clinton responded: “I respect his children … . I don’t agree with nearly anything else he says or does, but I do respect that.”

Trump, answering the same question, said: “I will say this about Hillary: She doesn’t quit. She doesn’t give up.”

The two candidates did shake hands at the end of the debate.

While the first debate ended in a lopsided declaration of victory for Clinton, Sunday’s encounter brought a more typical response from partisans on both sides. “I think Trump came here to knock Hillary off her game and he was unsuccessful,” said U.S. Rep. Lacy Clay, D-Mo. He called Trump “very rude, very uncivil” and “unpresidential.”

U.S. Rep. Jason Smith, R-Mo., said Trump did “very well” and may have helped tamp down the controversy over the tape. “More than an hour of talk was based on policies to move the country forward and on how to change Washington,” he said.

As for whether it will be enough to move him past Friday’s controversy, he said: “That’s up to the American people to decide, but he apologized. I think that was important.”