"She doesn't have the look. She doesn't have the stamina, I said she doesn't have the stamina, and I don't believe she does have the stamina," Trump said.
The debate moderator, NBC's Lester Holt, asked Trump to clarify what he meant when he said earlier this month that his Democratic rival didn't have "a presidential look."
"I just don't believe she has a presidential look, and you need a presidential look," Trump had told ABC News' David Muir
in an interview.
Clinton responded: "As soon as he travels to 112 countries and negotiates a peace deal, a cease fire, a release of dissidents, an opening of new opportunities in nations around the world, or even spends 11 hours testifying in front of a congressional committee he can talk to me about stamina."
Clinton, the first woman to be nominated as a candidate for a major political party in US history, pointed out Trump pivoted from saying she doesn't look like a presidential candidate to saying she doesn't have the stamina.
"He tried to switch from looks to stamina, but this is a man who has called women pigs, slobs and dogs
," Clinton said in response to Trump.
Trump defended the comments, which he said were about Rosie O'Donnell.
"I said very tough things to (O'Donnell), and I think everybody would agree that she deserves it and nobody feels sorry for her," Trump said. "But you want to know the truth, I was going to say something extremely rough
to Hillary, to her family, and I said to myself, 'I just can't do it.' "