Virtually impossible to replace him at this stage, say experts
Replacing Donald Trump as the Republicans' presidential nominee would face huge legal and logistical hurdles.
With only a month to go before November 8, it would be a massive stretch to substitute Trump for his running mate Mike Pence or anyone else, Republican strategists and US election experts said.
It is "virtually impossible to replace somebody in August, let alone October," Republican strategist Karl Rove said.
Making a change at the top of the ticket for one of the two major parties this close to Election Day would be without precedent in modern US presidential elections.
In 1972, Democratic presidential candidate George McGovern's running mate, Thomas Eagleton, was replaced after it was revealed that the vice presidential hopeful had been hospitalised for depression. Eagleton withdrew from the race in August of that year and was replaced by Sargent Shriver.
In 2000, Missouri voters faced a last-minute candidate change in the state's US Senate race after the Democratic challenger Mel Carnahan died in a plane crash, a month before the election. Carnahan's name remained on the ballot, however, and the dead man won the election. His widow, Jean Carnahan was appointed to fill the seat.
Republican party rules do not include a mechanism to involuntarily remove from the ticket a presidential candidate who has already been nominated.
Party leaders could try to pressure Trump into resigning by withdrawing financial support for his campaign and withholding logistical help. But Trump showed no sign last night of backing down.
A long history of crude comments
If Hillary Clinton can't satisfy her husband, what makes her think she can satisfy America? - Trump tweeted in April 2015. He later deleted the post.
It must be a pretty picture, you dropping to your knees. - Trump to a female contestant in 2013 on an episode of 'Celebrity Apprentice'.
Did Crooked Hillary help disgusting (check out sex tape and past) Alicia M become a US citizen, so she could use her in the debate? - Trump tweeted in September 2016. He was referring to former Miss Universe winner Alicia Machado, whom he publicly shamed for gaining weight.
It's certainly not groundbreaking news that the early victories by the women on 'The Apprentice' were, to a very large extent, dependent on their sex appeal. - Trump wrote in his 2004 book, 'How To Get Rich'.
All of the women on 'The Apprentice' flirted with me - consciously or unconsciously. That's to be expected. A sexual dynamic is always present between people, unless you are asexual. - Trump, also from 'How To Get Rich'.
You could see there was blood coming out of her eyes. Blood coming out of her wherever. - Trump in August 2015, referring to Fox News anchor Megyn Kelly.
Look at that face! Would anyone vote for that? Can you imagine that, the face of our next president? I mean, she's a woman, and I'm not s'posedta say bad things, but really, folks, come on. Are we serious? - Trump in a September 2015 interview with 'Rolling Stone', about then-primary rival Carly Fiorina.
It doesn't really matter what (the media) write as long as you've got a young and beautiful piece of ass. - Trump in an interview with 'Esquire Magazine' in 1991.
A person who's flat-chested is very hard to be a 10, OK? - Trump in an interview with shock jock Howard Stern in September 2005.