WASHINGTON (AFP) - White House rivals Hillary Clinton and Donald Trump set their sights on crucial battleground Florida on Tuesday (Oct 25), blitzing the diverse state as the clock ticks down on the tumultuous race for the US presidency.

With two weeks to go before the Nov 8 election, polls showed Democrat Clinton - who is vying to be America's first female president - dominating nationally and looking for a resounding mandate to govern the bitterly divided country.

Trump, his campaign wilting under a barrage of controversies, acknowledged that the White House will likely elude him if he doesn't win Florida and its 29 electoral votes.

"I think that's probably true," the Republican nominee said in a telephone interview with Fox News.

"I believe Florida is must-win. I think we're winning it, think we're winning it big," said the 70-year-old Manhattan real estate mogul.

Early voting began in Florida on Monday (Oct 24), an urgent reminder that candidates have little time left to make their case in the country's third most populous state, one with a wide mix of constituencies - retirees, Latinos and Bible Belt whites.

No one has forgotten that the 2000 US presidential election turned on Florida, where a virtual tie was decided in favor of George W. Bush by the US Supreme Court.

Poll averages show that Clinton, the 68-year-old former secretary of state, is ahead in the state by 3.8 percentage points, and nationally by 5.1 points, according to RealClearPolitics.

She was to make a campaign appearance in the afternoon at a college in southern Broward County near Fort Lauderdale, before going on to a fundraiser in Miami.

But Trump was first out of the blocks on Tuesday, taking aim at a sharp rise in health insurance premiums under President Barack Obama's signature health care reform.

"It's just blowing up," Trump said at an event with employees of a golf course he owns in Doral, Florida, vowing to "repeal and replace" Obamacare if elected.

He repeated that line of attack in tweets, and the phone interview with Fox News, brushing off a question about his recent threat to sue women who have accused him of making unwanted sexual advances.

"I would like to get off the subject, everybody brings that up. The fact is, that was a speech talking about Obamacare. We have to repeal it and replace it," he said.

The New York billionaire's standing in the polls has been hit hard, particularly among female voters, since the release of a 2005 video on which he is heard boasting of the fact that his celebrity allows him to grope and force himself on women.

Since then, about a dozen women have come forward with allegations of sexual misconduct.

At a campaign event in New Hampshire with Clinton on Monday, fiery liberal Senator Elizabeth Warren served notice on Trump that Democrats are not turning the page on his treatment of women.

"Nasty women have really had it with guys like you," Warren said, quoting a disparaging remark the Republican made about Clinton at their last debate.

"Nasty women are tough. Nasty women are smart. And nasty women vote," she said.

At a Monday fundraiser in La Jolla, California, President Barack Obama said he wants an overwhelming Clinton victory in order to send the message that Americans reject Trump's divisive rhetoric.

"We want to win big," Obama said. "We don't just want to eke it out, particularly when the other guy's already started to gripe about how the game is rigged."

With his path to victory narrowing, Trump has railed against the "phony" polls and appealed to voters to turn out, calling it a "once-in-a-lifetime opportunity" to reject the political elite."

"We're doing great in Ohio. We're doing great in Iowa. I think we're doing very well in New Hampshire," he said in the Fox News interview.

"Honestly I think we're doing really well all over. People want change. They are tired of incompetence," he said.

Trump pointed to what he described as long lines of early voters in Florida as a hopeful sign.

"I don't know what this means but they're wearing Trump hats and Trump buttons and Trump shirts. That is generally good news but you never know," he said.

Despite the expressions of confidence, a growing recognition that he may be facing defeat has crept into Trump's speeches.

"Make sure you get out and vote, or this whole thing, you know the movement that they're all talking about all over the world, it won't be the same, folks," Trump told an enthusiastic crowd in Tampa on Monday.

"We're not going to be able to do what we wanted to do."