Donald Trump says "win, lose or draw" he will be happy he gave his all in the race for the White House, as a poll finds his claims the election is "rigged" against him is resonating with voters.

Key points: Donald Trump pledges to do everything to win the presidency

Donald Trump pledges to do everything to win the presidency Poll finds 70pc of Republicans think Clinton win would be because of fraud

Poll finds 70pc of Republicans think Clinton win would be because of fraud Lawyers apply for campaign content to be barred from Trump University trial

The billionaire Republican nominee has for days been coy about whether he will accept the results of the election should Democratic rival Hillary Clinton beat him on November 8.

In comments seemingly moving away from his refusal to commit to accepting the result, Mr Trump told a rally in battleground state North Carolina he wanted to have no regrets about whether he worked hard enough to win the election.

"Win, lose or draw — and I'm almost sure if the people come out we're going to win — I will be happy with myself," he said.

"As I always say, I don't want to think if only I did one more rally, I would have won North Carolina."

During a debate with Mrs Clinton this week, the New York businessman refused to commit to accepting the outcome of the election if he loses, saying "I'll keep you in suspense".

His remarks challenged a cornerstone of American democracy and outraged Democrats and many Republicans.

Clinton preparing for possibility of Trump refusing to concede

Mrs Clinton said the refusal to make the commitment was "horrifying".

Her campaign is increasingly preparing for the possibility Mr Trump may never concede the election, should she win.

"I've got to figure out how we heal these divides," Mrs Clinton said in an interview with radio station WBTP.

"We've got to get together. Maybe that's a role that is meant to be for my presidency if I'm so fortunate to be there."

Mr Trump, who is lagging in opinion polls, has offered no widely accepted evidence to back up his vote-rigging claims, and numerous studies have shown that the US election system, which is run by the states, is sound.

A new Reuters/Ipsos poll showed only half of Republicans would accept Mrs Clinton as their president, and nearly 70 per cent of them said a Democratic Party victory would be because of illegal voting or vote rigging.

Mr Trump stepped up allegations that the election was being rigged as he faced accusations — which he has strongly denied — that he made improper sexual advances to women, including groping and kissing, over decades.

Mrs Clinton's lead over her main rival in national opinion polls has grown in recent weeks with an average of polls by RealClearPolitics showing her currently 6.3 points ahead at 48.5 per cent support to Mr Trump's 42.2 per cent.

Trump seeks to distance campaign from Trump University trial

Meanwhile, lawyers for Mr Trump have asked a judge to bar accusations about his personal conduct that have arisen during the election campaign from an upcoming civil trial over Trump University.

Students at Trump University claim they were defrauded by its real estate seminars.

In a court filing late on Thursday, attorneys for Mr Trump said evidence and statements from the election campaign should be barred from trial because they could unfairly prejudice the jury.

The trial is set to begin on November 28.

Evidence including Mr Trump's campaign speeches, tweets, his tax issues and controversy over his personal charity should not be considered by jurors, the filing said.

All audio and video recordings publicised during the campaign should also be barred, the filing said, along with evidence about Mr Trump's beauty pageants, casinos and corporate bankruptcies.

"Before trial begins in this case, prospective members of the jury will have the opportunity to cast their vote for president," Mr Trump's lawyers wrote.

Mr Trump's lawyers also asked US District Judge Gonzalo Curiel to exclude evidence about students' finances from the trial, saying the affordability of Trump University was not relevant to the trial.

A spokeswoman for the plaintiffs declined to comment.

Mr Trump set off an uproar earlier this year when he accused the judge of being biased against him because of the Mr Trump's pledge to build a border wall between the US and Mexico.

Judge Curiel was born in Indiana and is of Mexican descent.

Reuters