Donald Trump accused Hillary Clinton's campaign of orchestrating a series of accusations by women who said the businessman made unwanted sexual advances against them.
In the third and final presidential debate with Democratic rival Mrs Clinton, Mr Trump said all of the stories were "totally false" and suggested Mrs Clinton was behind the charges. He called her campaign "sleazy".
"I think they either want fame or her campaign did it, and I think it's her campaign," Mr Trump said.
"I didn't even apologise to my wife who is sitting right here because I didn't even do anything," he added.
Mrs Clinton said the women came forward after Mr Trump said in the last debate he had never made unwanted advances on women.
In a 2005 video, Mr Trump was recorded bragging about groping women against their will.
"Donald thinks belittling women makes him bigger. He goes after their dignity, their self-worth and I don't think there is a woman anywhere who doesn't know what that feels like," Mrs Clinton said. She cited other minorities she said Mr Trump had maligned.
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"This is a pattern. A pattern of divisiveness, of a very dark and in many ways dangerous vision of our country where he incites violence, where he applauds people who are pushing and pulling and punching at his rallies. That is not who America is," she said.
In a personal attack on Mrs Clinton, Mr Trump said: "The only thing you have over me is experience but it's bad experience.
"If you became president this country is going to be in some mess."
Mr Trump refused to say that he would accept the outcome of the 8 November US presidential election, leaving open the possibility he would challenge the ultimate outcome.
He said he would wait to decide whether the outcome was legitimate.
Mr Trump's remarks came after making claims this week of "large-scale voter fraud".
"I will look at it at the time," he said of the 8 November election.
The billionaire tycoon said the media was "so dishonest" and had "poisoned the minds of voters".
Of Mrs Clinton, he added: "She shouldn't be allowed to run. It's crooked. She's guilty of a very serious crime.
"Just in that respect I say it's rigged. She should never have been allowed to run for the presidency," he said.
"I will tell you at the time, I will keep you in suspense," Mr Trump said.
Mrs Clinton responded: "Let's be clear about what he is saying and what that means: He is denigrating, he is talking down our democracy and I for one am appalled that someone who is the nominee for one of our two major parties would take that position."
