Clinton and Trump chase last-minute support on US election eve

The FBI's Comey sent shockwaves through the race when he told Congress on Sunday that investigators had reviewed recently discovered emails and found no reason to change their July finding that there was no criminal wrongdoing in Clinton's use of a private email server, rather than a government system, while she was the top US diplomat from 2009-2013.

Trump, who drew wide criticism last month when he said the election was rigged against him and that he would not yet commit to respecting the outcome, questioned the thoroughness of the FBI review and said the issue would not go away.

Tammy Regis, 42, a disabled Army veteran who served in Iraq and now lives in Palmetto, Florida, said she would not trust the outcome if Clinton wins.

"If she wins, no I won't. I just think it's really shady," Regis said, adding that she did not know why Comey "flip-flopped" on Clinton's emails.

Since entering the race in 2015 and then seeing off 16 Republican rivals to win the party nomination, Trump has challenged political norms with bombast, personal attacks and unorthodox policies, including proposals to bar Muslims from entering the United States and build a wall on the southern border to keep immigrants from entering illegally.

In October, his campaign was rocked by the circulation of a 2005 video in which he boasted about groping women.

While such controversies have given Clinton the edge among women and minorities, Trump enjoys solid support among non-college educated whites. For both candidates, turning that support into actual votes is critical to building the 270 electoral votes needed to win.

The make-up of Congress is also at stake on Tuesday and as candidates running for the U.S. Senate and House of Representatives wrapped up their campaigns Republicans were seen as making some gains in their quest to hold majority control of both chambers.