WASHINGTON/RALEIGH, N.C. (REUTERS) - A top adviser to Donald Trump acknowledged on Sunday (Oct 23) that the Republican presidential candidate was lagging behind rival Hillary Clinton, as the Democratic nominee pressed a strategy of encouraging early voting in key battleground states.
Mr Trump's campaign manager Kellyanne Conway said Mrs Clinton had "tremendous advantages," including a large campaign war chest that had allowed her to spend millions on television ads ahead of the Nov 8 election.
"We are behind," Ms Conway said on NBC's Meet the Press. But she added the Trump campaign was looking to sway undecided voters not ready to support Mrs Clinton.
As the polling gap has widened, Mr Trump has said repeatedly the election is being "rigged" against him. He has not offered evidence and numerous studies have shown that the US election system, which is decentralised and run by the states, is sound.
At last week's debate with Mrs Clinton, Mr Trump challenged a cornerstone of American democracy by refusing to commit to honoring the result of the US election. "What I'm saying is that I will tell you at the time. I'll keep you in suspense. OK?" Mr Trump said.
In the aftermath of the debate, Mr Trump said he would accept the election outcome "if I win".
Mrs Clinton, speaking at a campaign rally in Raleigh, North Carolina, one of seven key swing states the candidates will focus on in the remaining two weeks until the election, blasted Mr Trump's continued refusal to pledge to accept the outcome of the race, encouraging voters to turn out and cast their ballots early.
"He refused to say that he would respect the results of this election, and that is a threat to democracy," she said.
"The peaceful transition of power is one of the things that makes America America."
"From now until Nov 5, you can vote early at any voting location in your county. And you know, this is a big deal," Mrs Clinton told about 3,500 supporters.
The latest Reuters/Ipsos poll released on Friday had Mrs Clinton leading Mr Trump by 4 percentage points, and the most recent State of the Nation project showed Mrs Clinton with a 95 per cent chance of winning the 270 Electoral College votes needed to secure the presidency.
An ABC News poll released on Sunday morning had Mrs Clinton leading with 50 per cent of likely support, compared with Mr Trump's 38 per cent. The poll found that the number of Republicans who said they were likely to vote fell 7 percentage points from mid-October.
As Mr Trump battled to win over undecided voters, efforts by advisers and members of his inner circle to downplay his remarks about the integrity of the election indicated he would come under significant pressure to accept the election results if he were to lose.
Republican Party chairman Reince Priebus said that by asking Mr Trump to agree to concede, the media were making an extraordinary request. He said Mr Trump would only fight if the election were close and was not trying to dispute a fair election.
"That's not quite what he's saying. What he's saying is he wants to reserve all options and if there is ground for a recount, I'll reserve all options," Mr Priebus said on CBS's Face The Nation.
Mr Trump's son Eric said on Sunday that Mr Trump would "100 per cent" accept the results of the election if the outcome is "fair".
"I think what my father is saying is, 'I want a fair election'," Mr Eric Trump said on ABC's This Week. "If it's a fair outcome, he will absolutely accept it. There's no question about that."
Mr Trump was planning to hold a rally in Naples, Florida, on Sunday evening and plans to campaign in the state for the next three days. Recent opinion polls show a tight race in the state, with Mrs Clinton leading by 47 per cent to 43 per cent.
On Sunday, Mr Trump picked up his first endorsement of the general election from a major newspaper when the Las Vegas Review-Journal backed his candidacy. The newspaper is owned by Republican mega-donor Sheldon Adelson, who has been reluctant to donate to Mr Trump. In 2012, Mr Adelson spent about US$150 million (S$209 million) trying to help elect Republican Mitt Romney.