Donald Trump stormed into traditionally Democratic territory on Tuesday in a last-ditch bid to open up a path to an unlikely White House win, buoyed by a shock new poll showing him edging ahead of Hillary Clinton.
If Clinton was rattled by the dramatic tightening in the numbers a week before Election Day, she did not show it, barnstorming through key swing state Florida and once again hammering Trump's attitude to women.
Forecast models still show the 70-year-old Republican property mogul facing an uphill battle to win enough states to secure an electoral college victory over the 69-year-old Democratic frontrunner on November 8.
But he received a boost on Tuesday when an ABC News/Washington Post tracking poll showed him leading his rival, embroiled in an FBI probe into her email history, by 46 to 45 percent.
This was enough to spook the markets, which had expected the former secretary of state to comfortably defeat a populist Republican economists fear could plunge the world into recession.
US stocks closed down 0.7 percent and the Vix Volatility or "fear index" jumped to its highest level since Britain voted to leave the European Union.
Lewd comments, Russia and emails
But no matter how close Trump comes in the popular vote, in order to win the White House, he must seize at least one traditionally Democratic state as well as several swing states and the Republican heartland.
On Tuesday, that quest brought the brash billionaire to Wisconsin, which in 2012 voted 53-46 percent to give its 10 electoral college votes to President Barack Obama and return him to the White House.
Earlier, the Manhattan real estate mogul went to the town of King of Prussia in Pennsylvania -- another crucial battleground -- to deliver a policy speech .
"Our tax plan will provide a 35 percent tax cut to middle class families with two kids," he told supporters. "Our middle class has not been properly respected. That I can tell you."
If Trump can win both the safe Republican states and those considered up for grabs -- itself a challenge -- Wisconsin's 10 votes could put him over the 270 threshold and force Obama to hand him the keys to 1600 Pennsylvania Avenue.
But this remains a long shot. The New York Times' statistical model gives Clinton an 88 percent chance of winning, while respected data tracking website FiveThirtyEight says she has a 74 percent chance of victory.
Nevertheless, the tumultuous presidential race -- which has of late featured footage showing Trump boasting of sexual assault and claims of Russian interference in the contest -- may have a few twists and turns left in store.
On Monday, Trump was hit by fresh allegations in a detailed report by The New York Times that he not only dodged paying income tax, but did so in a legally dubious way that has since been outlawed.
This may not be enough to turn attention away from stories about a revived FBI investigation into whether Clinton put US secrets at risk by using a private email server while serving as secretary of state.
Insulting 'Miss Piggy'
Both ongoing scandals were bubbling under the surface when Clinton appeared in Florida to hammer Trump's fitness for office and -- in particular -- his treatment of women.
Clinton was introduced by Alicia Machado, a former Miss Universe whom Trump, then the owner of the pageant, humiliated by mocking her post-victory weight gain and calling her "Miss Piggy."
"Can we just stop for a minute and reflect on the absurdity of Donald Trump finding fault with Miss Universe?" Clinton snorted. Trump's doctor says he is more than overweight at 236 pounds (107 kilos).
"What about our girls? What happens to their confidence, their sense of self-worth?" Clinton demanded, warning against electing a president "who insults more than half the population."
And she pivoted to the notorious tape where Trump is overheard on a hot mic bragging about being able to grope women and get away with because he is a star.
"And I have to tell you, since that tape came out 12 women have come forward to say: 'What he said on that tape is what he did to me'," Clinton said. Trump denies these allegations.
Clinton's campaign has spent three days berating FBI director James Comey for revealing to lawmakers that the bureau is looking anew at her use of a private email server while at the State Department.
Clinton and her supporters were furious that Comey made his announcement without providing any new evidence of wrongdoing, but her campaign insists the scandal has not torpedoed her candidacy.
"If anything, it's angered our supporters and been a motivating factor, but it doesn't seem to be affecting the overall vote," he said, writing off the new tracker results as "bad polling."
Obama and Vice President Joe Biden both hit the campaign trail for Clinton on Tuesday and have a full schedule for the week, hoping to push her past Trump in the homestretch.
Obama -- who was in Ohio -- is having what his spokesman called a "heck of a good time" making the case for Clinton, calling his full schedule "an indication of exactly how big he thinks the stakes are in this election."