Republican Donald Trump has said he would accept a "clear" election result but reserved the right to file a legal challenge, clarifying his stance a day after he refused to promise he would trust the outcome if he loses on 8 November.

"Of course, I would accept a clear election result, but I would also reserve my right to contest or file a legal challenge in the case of a questionable result," Mr Trump said at a rally in Ohio.

Asked yesterday at his final debate with Democrat Hillary Clinton if he would accept a losing outcome, Mr Trump said he would "keep you in suspense."

"I'll look at it at the time," Mr Trump said. "What I've seen is so bad." 

This week Mr Trump made claims of "large-scale voter fraud". 

An angry Mrs Clinton responded with incredulity to the highly controversial charge, saying, "I, for one, am appalled that somebody who is the nominee of one of our two major parties would take that kind of position."

His democratic rival stressed that citizens accept election outcomes in a democracy but called Mr Trump's reaction to say it is rigged was "funny and also really troubling".

"This is horrifying," Mrs Clinton said.

Mrs Clinton said Mr Trump has a pattern of saying competitions and cases he loses are rigged including when he did not win an Emmy for his TV reality show The Apprentice. To which Mr Trump said he should have won the Emmy.

Fitness to be president

Mrs Clinton accused Mr Trump of being the most dangerous White House candidate in modern history, ending a sharp debate exchange about their fitness to serve as president.

After Mr Trump used statements by Mrs Clinton's primary rival Bernie Sanders and Mrs Clinton's campaign chairman John Podesta against her, she retorted: "You should ask Bernie Sanders who he is supporting.

He said you are the most dangerous person to run for president in the modern history of America. I think he's right.

Mr Trump described claims he sexually assaulted a number of women as "totally false" and accused Hillary Clinton's campaign team of creating the allegations.

"I didn't even apologise to my wife who is sitting right here because I didn't even do anything," he added.

"These women ... I think they either want fame or her campaign did it. And I think it's her campaign."

Mrs Clinton said: "Donald thinks belittling women makes him bigger. He goes after their dignity and self-worth."

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."

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.

The billionaire tycoon said the media was "so dishonest" and had "poisoned the minds of voters".

In contrast to the fiery personal attacks of the first two debates, Mrs Clinton and Mr Trump had a sharp but issues-based exchange on abortion, gun rights and immigration to start the 90-minutes showdown.

While neither candidate struck a devastating blow against their opponent, the debate will be remembered for Mr Trump's failure to adhere to historical protocol in agreeing to accept the outcome of the election whatever that may be.

Trump campaign is 'unprecendented'

Professor Robert Schmuhl from the University of Notre Dame has said Donald Trump's campaign has been unprecedented.

He described Donald Trump as a marathon runner, "off by himself and out on his own" in relation to the Republican party, signifying that the importance of a personality in American politics can be divorced from the party.

Professor Schmuhl questioned the extent to which Mr Trump being alone will affect the races in the House of Representatives and the Senate.

He said Hilary Clinton is doing well in the "battle-ground" states, adding that she is beginning to make a stand in states where the Democrats have not won in recent years.

But he questioned whether there is a silent and secret vote for Donald Trump, liking it to a possible Brexit.

Key Points:  Abortion, Putin’s puppet and bad hombres

Watch the debate in under 10 minutes

Media reaction to the final debate

US Supreme Court and abortion

Fitness to serve as US president

Immigration and the wall with Mexico