Republican vice presidential candidate Mike Pence has vigorously defended running mate Donald Trump against allegations of sexual misconduct and promised evidence casting doubt on the claims is about to be released.

Trump's campaign has been scrambling to recover from the release a week ago of a 2005 video in which he brags about groping women. Multiple women subsequently went public with allegations of sexual misconduct against the New York real estate magnate, who has denied the claims.

Pence, the conservative Indiana governor, said on Friday that Trump had assured him personally the allegations were false.

"Before the day is out, there'll be more evidence publicly that calls into question these latest allegations," Pence said in an interview with CBS "This Morning."

"Stay tuned. I know there's more information that's going to be coming out that will back his claim that this is all categorically false."

Pence told NBC's "Today" show that the evidence was just "hours" away from being made public.

With his numbers dropping in opinion polls before the November 8 election, Trump told supporters at a rally in Florida on Thursday that accusations he groped women in a series of incidents going back to the 1980s were part of a coordinated attempt to keep him from the Oval Office.

"I do believe him," Pence insisted on CBS.

In several morning television interviews on Friday, Pence tried in vain to shift the debate to Democratic presidential candidate Hillary Clinton, her family's charity and information from the hacked emails of her campaign manager, John Podesta.

The New York Times reported on Wednesday night that two women said they had endured sexual aggression from Trump, and several others made similar allegations in other media outlets.

The New York Times said on Thursday it stood by its story and rejected charges the article was libelous after a lawyer for Trump threatened legal action and demanded a retraction.

The allegations roiled an unorthodox campaign that has been pockmarked by controversial Trump proposals including building a wall along the Mexican border and temporarily banning Muslims from entering the country. The candidate's demeaning comments about women throughout the campaign has drawn criticism among a group of voters his campaign wants and needs to court.

They also drew an impassioned denunciation of Trump from popular first lady Michelle Obama, who was campaigning for Clinton in New Hampshire on Thursday.

"This is not normal. This is not politics as usual. This is disgraceful. It is intolerable," the first lady said. "I know it's a campaign, but this isn't about politics. It's about basic human decency. It's about right and wrong."