Donald Trump has defended his obscene remarks about groping women by launching a blistering attack against Hillary Clinton and her husband.
The Republican nominee denied ever sexually assaulting women, but turned his fire on ex-President Bill Clinton in a bitter US presidential debate.
"There's never been anybody in the history of politics that has been so abusive to women," he said.
Hillary Clinton refused to address his comments about her husband.
Mr Trump's attack on the Clintons came after moderator Anderson Cooper asked him about a 2005 video recording released on Friday that revealed Mr Trump bragging about groping women.
But when pressed on whether he had engaged in sexual misconduct with any women, he denied doing so and instead focused on Mr Clinton's previous indiscretions.
No criminal charges have been brought against Mr Clinton in any allegations of sexual assault.
Mrs Clinton said the explosive video, which has sparked an exodus of Republicans denying support to their presidential nominee, showed who Mr Trump really was.
"With prior Republican nominees, I disagreed with them," she added, "but I never questioned their fitness to serve.
"I think it's clear to anyone who heard [the video] that it represents exactly who he is."
When the two took to the stage in St Louis for their second of three debates, they did not shake hands, striking a bitter tone that would continue throughout.
Mr Trump said if he won, he would appoint a special prosecutor to investigate Mrs Clinton and she would be in prison over her private email arrangements.
"Everything he just said is absolutely false but I'm not surprised," she responded. "It's just awfully good that someone with the temperament of Donald Trump is not in charge of the law in our country."
"Because you'd be in jail," he interrupted.
Mr Trump also said his Democratic rival "has tremendous hate in her heart" while criticising her for referring to his supporters as "deplorables".
Mrs Clinton said she apologised for the comment, adding: "My argument is not with his supporters, it's with him, about the hateful and divisive campaign he has run."
The two also sparred on the conflict in Syria, Russian aggression, Trump's refusal to release his tax returns and his plan for the "extreme vetting" of immigrants arriving from countries with links to terrorism.
The evening concluded when an audience member asked the candidates to say one positive thing about each other.
Mrs Clinton said his children were a great reflection of him while Mr Trump called his opponent "a fighter" who never gives up.
An hour before the debate began, Mr Trump appeared at a press conference with women who accused Bill Clinton of sexual misconduct.
He joined three women who allege the former president sexually assaulted them and called the women "very courageous".
The Republican was under immense pressure after making obscene comments about women in the video.
At least 33 senior Republicans - including senators, members of Congress, and state governors - have withdrawn their support since the video surfaced on Friday.
Analysis - Anthony Zurcher, BBC News, St Louis
Donald Trump entered this debate threatening to unload every bit of malicious allegations and rumours on Hillary Clinton. And he did.
Accusations of Bill Clinton's sexual impropriety? Check. Her work as a public defender representing a rapist? Yup. He even tied it up in a bow by remarking that his Democratic opponent should be in jail.
Mrs Clinton said she would take the high road, but she did get in her shots as well, saying the illicit video of Mr Trump's lewd comments showed who he really is.
And then, after that nuclear exchange, the debate chugged along - with Mr Trump often gaining the upper hand. If his weakness is policy knowledge, there were few opportunities where his shortcoming were exposed.
Instead, there was plenty of time for Mrs Clinton to offer a yet another muddled answer on her email server and essentially confirm that the Wikileaks hacked speech excerpts are accurate. Mr Trump offered word salads in answers about healthcare reform and Syria policy. If anything, from there the debate was a draw.
With Mrs Clinton ahead right now, a draw will probably suit her just fine. But it wasn't the knock-out blow her supporters probably hoped for.
What else came up at debate?
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Mr Trump said he had not paid federal income tax in 18 years because he knew the tax code well
He constantly complained to the moderators that he was not getting fair treatment
On Syria, Mrs Clinton said she would not advocate the use of US ground forces
She promised that no-one making less than $250,000 will pay higher taxes but richer people will
Mr Trump also admitted he and running mate Mike Pence disagreed about use of force in Syria
But he refused to answer when moderator Martha Raddatz pressed him for a military strategy
Mrs Clinton also defended controversial remarks she made in a private speech that was made public in leaked emails on Saturday.
The transcript had revealed she said a politician has a public and private position, but at the debate she said she had watched a film about Abraham Lincoln and was referring only to what he had done.
So who are the women?
Mr Trump appeared with Paula Jones, a former Arkansas state employee who settled a sexual harassment suit against Mr Clinton for $850,000 in 1999 with no admission of guilt.
Juanita Broaddrick, who claimed Mr Clinton raped her in a hotel room in 1978, also appeared with Mr Trump.
Mr Clinton has denied the claim through his lawyer and no charges have ever been brought against him.
The third woman was Kathleen Willey, a former White House aide who said Mr Clinton groped her in his office in 1993, but had previously said it never happened.
Mr Clinton has also denied this claim.
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Donald Trump, centre, sits with, from right, Paula Jones, Kathy Shelton, Juanita Broaddrick, and Kathleen Willey
Kathy Shelton, a fourth woman who spoke, encountered Mrs Clinton in a criminal case when she was 12 years old.
Early in Mrs Clinton's legal career, she was appointed to defend Ms Shelton's rapist, despite objections, and had his sentence reduced to a lesser charge.
Years later, an audio tape emerged of Mrs Clinton speaking with a reporter, in which she can be heard laughing about the case.
During one instance, she laughed after explaining that her client had passed a lie detector test, which convinced her to never trust them again.