The stage is set prior to the third and final 2016 U.S. presidential campaign debate between Democratic presidential candidate Hillary Clinton and her Republican rival Donald Trump, at UNLV in Las Vegas, Nevada, U.S., Oct. 19, 2016.
The stage is set prior to the third and final 2016 U.S. presidential campaign debate between Democratic presidential candidate Hillary Clinton and her Republican rival Donald Trump, at UNLV in Las Vegas, Nevada, U.S., Oct. 19, 2016.

WASHINGTON - Republican Donald Trump and Democrat Hillary Clinton are heading to their third debate late Wednesday in their acrimonious run for the U.S. presidency, the last time millions of Americans will have a chance to see them square off as they trade taunts and policy positions on a wide range of issues.

Clinton, the one-time U.S. secretary of state looking to become the country's first female president, will show up on the debate stage in Las Vegas, Nevada, with a growing lead in political polls over Trump, the brash real estate tycoon running for elected office for the first time. It is perhaps his last best chance to cut into her seven-percentage-point advantage less than three weeks before the November 8 election.

Both have declared each other as unfit to become the country's 45th president when President Barack Obama leaves office in late January. They traded barbs on their Twitter accounts ahead of their high-stakes face-to-face encounter.

"Even if Trump's bullying, bigotry, and misogyny weren't disqualifying, his policies would be," Clinton said.

Trump said, "If we let Crooked (Hillary) run the govt, history will remember 2017 as the year America lost its independence. Drain the Swamp."

Fox News television anchor Chris Wallace plans to quiz Trump and Clinton about six topics: immigration, social benefit entitlements for Americans and the country's long-term debt, Supreme Court appointments, the economy, foreign policy, and each candidate's fitness to serve as president. Both candidates will get two minutes to answer a question and then to respond to the other, with Wallace asking follow-up questions.

Trump and Clinton have sparred on the debate stage two times already, with credible polls showing she won both times. But analysts thought Trump performed better in his second match-up with her 10 days ago and could, with a strong debate performance and pointed attacks on her, give undecided and wavering Clinton supporters new reason to consider casting a ballot for him. Some U.S. states are already holding early voting.

Republican presidential nominee Donald Trump speak
Republican presidential nominee Donald Trump speaks to Democratic presidential nominee Hillary Clinton during the second presidential debate at Washington University in St. Louis, Sunday, Oct. 9, 2016.

Challenges for both candidates

Both candidates are facing new questions since the last time they met.

Disclosures from Clinton's tenure as the country's top diplomat from 2009 to 2013 and her use of a private, unsecured email server rather than a secured government server continue to raise questions for some voters about her judgment and honesty. Government investigators concluded that she was "extremely careless" in her handling of national security material in her email chains, but that no criminal charges were warranted.

She has on numerous occasions conceded she made a mistake in using a private email server based inside her New York home, but has rejected Trump's claims she endangered national security. This week, a new document released by the Federal Bureau of Investigation depicted one of Clinton's State Department aides attempting to get a classified document downgraded to unclassified in an apparent effort to support Clinton's claim that she never knowingly sent or received classified material in her chain of emails.

DEM 2016 Clinton Emails
FILE - In this Oct. 18, 2011, photo, then-secretary of state Hillary Clinton checks her smartphone aboard a C-17 military plane en route to Tripoli, Libya. Clinton's handling of emails has figured prominently in the presidential campaign.

Thousands of emails hacked from the computer of her campaign chief John Podesta and disclosed by WikiLeaks are posing other problems for Clinton. Among the leaks were friendly overtures to Wall Street she made in three 2013 speeches to executives at the investment banking firm of Goldman Sachs for which she was paid $675,000.

Trump's declining fortunes in national polls stem from the disclosure two weeks ago of a 2005 tape of him riding on a bus on a Hollywood back lot in which he made lewd comments about women and boasted he could grope them with impunity because of his celebrity status.

Trump, once the host of a television reality show, apologized at the second debate for his crude remarks, calling them "locker room talk," and denied that he actually made unwanted advances on women. But within days, at least nine women claimed Trump had made untoward sexual overtures on them over several decades, often kissing and groping them in much the same way he described on the tape.

He called the women's accounts fabrications that never happened, but several of the women described his advances contemporaneously to friends and co-workers shortly after they occurred.

APTOPIX Campaign 2016 Trump
Republican presidential candidate Donald Trump kisses a "Women for Trump" sign during a campaign rally in Lakeland, Florida, Oct. 12, 2016. Trump's poll numbers sank following allegations by numerous women that he had made unwanted sexual advances toward them.

Trump's wife Melania defended her husband in two television interviews this week and said she had accepted his apology for his taped remarks. Trump and his wife have blamed the U.S. national news media in concert with the Clinton campaign for the continuing controversy over the comments.

In recent days, Trump, while presenting no evidence, has claimed that the outcome of the election is "rigged" and that voter fraud will turn the election in Clinton's favor. Obama, at a White House news conference Tuesday, said Trump should "stop whining" and instead make his case to U.S. voters why he should be elected.