By Emily Stephenson and Amanda Becker

NEWTOWN, Pa./CLEVELAND (Reuters) - Republican presidential candidate Donald Trump gained on his Democratic rival Hillary Clinton among American voters this week, cutting her lead nearly in half, according to Reuters/Ipsos polling released on Friday.

The polling data showed Trump's argument that the Nov. 8 election is "rigged" against him has resonated with members of his party.

"Remember folks, it's a rigged system," Trump told a Pennsylvania rally on Friday. "That's why you've got to get out and vote, you've got to watch. Because this system is totally rigged."

Clinton led Trump 44 percent to 40 percent, according to the Oct. 14-20 Reuters/Ipsos poll, a 4-point lead. That compared with 44 percent for Clinton and 37 percent for Trump in the Oct. 7-13 poll released last week.

An average of national opinion polls by RealClearPolitics shows Clinton currently 6.2 percentage points ahead at 48.1 percent support to Trump's 41.9 percent.

Trump's campaign was thrown into crisis after a 2005 video released earlier this month showed him bragging about groping and kissing women. He has since faced accusations - which he has said are "absolutely false" - that he made improper sexual advances to women over decades.

The Reuters/Ipsos survey found 63 percent of Americans, including a third of Republicans, believe the New York real estate mogul has committed sexual assault in the past.

Reuters contacted a few of the poll respondents who said they felt that Trump had likely "committed sexual assault" but were still supporting his candidacy. Their answers were generally the same: Whatever Trump did with women in the past is less important to them than what he may do as president.

At a Trump rally in Fletcher, North Carolina, Harold Garren, 75, said he was skeptical of complaints from women about Trump's behavior. "I don't believe all of this 30 years later, no," Garren said.

Garren also shrugged off Trump's lewd bragging about women, caught on the 2005 tape. "I've used that barnyard language myself," Garren said, clarifying that it was when he was younger and before he knew better.

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Both candidates spent Friday in battleground states, where the vote could swing either way. Clinton, 68, campaigned in Ohio, while Trump, 70, was in North Carolina and Pennsylvania.

Trump, his voice lacking some of its usual energy in his third rally in one day, told voters in Newtown, Pennsylvania they had to vote or else he would have wasted a lot of "time, energy and money."

Trump is planning to give a speech Saturday in Gettysburg, Pennsylvania, in which he will kick off his closing argument for voters and preview his first 100 days in office, a Trump campaign aide said.

'RIGGED' MESSAGE FINDS SUPPORT

Trump has been coy about whether he will accept the results of the election should Clinton beat him.

The Reuters/Ipsos data showed only half of Republicans would accept Clinton as their president, and nearly 70 percent of them said a Clinton victory would be because of illegal voting or vote rigging.

Trump's crowd chanted "Lock her up!" at a rally in Johnstown, Pennsylvania after he declared Clinton a "corrupt globalist," a reference to campaign documents released by WikiLeaks in which Clinton was quoted advocating free trade and open borders.

After the chant went around the room for several seconds, Trump responded, "Don't worry, that whole thing will be looked into."

The New York businessman's assertion that the election is being rigged and his refusal to commit to accepting the outcome of the election if he loses has challenged a cornerstone of American democracy and outraged Democrats and many Republicans.

Asked if he would commit to a peaceful transition of power during Wednesday's debate, Trump replied: "What I'm saying is that I will tell you at the time. I'll keep you in suspense. OK?"

In Ohio on Friday, Clinton called his refusal unprecedented. "Now make no mistake: by doing that, he is threatening our democracy," she told a rally in Cleveland.

"But we know in our country the difference between leadership and dictatorship, right? And the peaceful transition of power is one of the things that sets us apart," Clinton said.

Trump has offered no widely accepted evidence to back up his claims of vote-rigging. Numerous studies have shown that the U.S. election system, which is run by the states, is sound.

Trump told an earlier rally in Fletcher, North Carolina, that he wanted to have no regrets about whether he worked hard enough to win the election, and urged followers to get out to vote.

"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. "We have to work, we have to get everybody out there.”

(Additional reporting by Doina Chiacu, Ginger Gibson and Susan Heavey; Writing by Alistair Bell and Roberta Rampton; Editing by Jonathan Oatis and Andrew Hay)