Last-minute polling suggested the president has enough of an edge in several key swing states to secure the 270 electoral college votes needed to win the election.
Team Romney disputes much of the polling, saying its internal numbers suggest the Republican presidential hopeful is on the road to victory.
Romney's campaign officials were upbeat on Monday, telling reporters they're "very, very optimistic about our chances." The candidate was equally cheerful at a rally in Florida, albeit repetitive.
"Tomorrow we begin a new tomorrow, tomorrow we begin a better tomorrow," he said in Orlando.
"This nation is going to begin to make a change for the better tomorrow ... We can begin a better tomorrow tomorrow, and with the help of the people of Florida that's exactly what's going to happen."
Romney intends to continue campaigning right into election day, planning stops in Pennsylvania and Ohio even as voters are making their way to the polls.
A hoarse Obama, meantime, was in the Midwest on Monday and was slated to make his final stop in Iowa later in the day before heading to his hometown of Chicago to await the election's outcome.
After a gruelling few weeks of non-stop campaigning, the president sounded at times as though he'd just smoked several packs of cigarettes.
He appeared at a rally in Wisconsin after rock icon Bruce Springsteen warmed up his supporters. Springsteen and rapper Jay-Z later did the same for the president in Columbus, Ohio.
"You know where I stand," the president told the Wisconsin audience.
"You know what I believe. You know I tell the truth. And you know that I'll fight for you and your families every single day as hard as I know how."
Wisconsin is among seven states considered battlegrounds, meaning they've been neither reliably Democrat nor Republican in recent presidential elections. Colorado, Iowa, Ohio, Virginia, Florida and New Hampshire are the other swing states, while Nevada and North Carolina are also in play this year for both Obama and Romney.
All eyes are on Ohio, however, the crown jewel in the race. No Republican has won the presidency without the so-called Buckeye State, and the path to victory becomes significantly more onerous for both Obama and Romney if they lose there on Tuesday.
Four new Ohio polls released on Monday, just hours before Americans began heading for the ballot boxes, showed Obama ahead of Romney, mostly by narrow margins.
And the final Washington Post/ABC News daily tracking poll also suggested the president had pulled out of his dead heat with Romney nationally. Fifty per cent of likely voters said they backed Obama while 47 supported his challenger.
The president's improved showing in a slew of recent surveys suggests his response to mega-storm Sandy last week has won him crucial support in swing states. Most of those surveyed have given Obama high marks when asked about his handling of federal relief efforts.
Perhaps not surprisingly, Obama has been exuding confidence in recent days, maintaining a packed schedule of campaign stops that have featured some moments of levity.
That included a brief onstage shimmy on Sunday in Ohio when Stevie Wonder appeared with him at a campaign event and sang "Sign, Sealed, Delivered" — Obama's 2008 campaign anthem.
His campaign also revealed on Monday that Obama planned to observe his most sacred election day ritual on Tuesday by playing basketball in Chicago with his longtime pal, Reggie Love.
Obama has almost always played hoops on election days, but he skipped the ritual on the morning of the 2008 New Hampshire primary — and subsequently lost to Hillary Clinton.
"We made the mistake of not playing basketball once," Robert Gibbs, a key member of Obama's re-election team, said Monday. "We won't make that mistake again."
For all the superstitions and swing state surveys, however, the 2012 election has been a battle over grand themes, including the role of government in the lives of citizens and the plight of the middle class.
Obama has been vilified by Republicans for a tepid economic recovery following the financial meltdown that took stubborn hold of the United States just as he won the White House in 2008.
They've also accused him of being a socialist, saying he's expanding government and creating a welfare state while raising taxes and running up the national debt to levels they consider obscene.
In fact, Obama has cut taxes and shrunk government during his four years in office, slashing more than half a million federal jobs since 2009.
His predecessor, George W. Bush, ran up the debt to unprecedented levels while financing two overseas wars. The billions Obama has spent in bailouts and economic stimulus measures are credited by many economists with putting the brakes to a full-fledged depression.
Democrats, meantime, have warned Americans that Romney and his running mate, Paul Ryan, will slash cherished entitlement programs, including Medicare, and push through 1950s-era social policies on abortion and contraception.
They also say he'll roll back Obama's Wall Street regulations to the relatively lawless state of affairs that allowed the financial meltdown to happen in the first place.
Team Obama has also mocked Romney's proposals to cut taxes across the board, increase defence spending and dramatically reduce the national debt as mathematically impossible, and insist the middle class will ultimately pay the price under a Republican presidency.
And yet every bit as important as who wins the White House is who wins the House of Representatives and the Senate. Congress, after all, is more powerful than the executive branch in terms of bringing to life — or killing — a president's legislative hopes and dreams.
Most polls suggest the makeup of Congress will remain relatively unchanged, with Republicans maintaining control of the House of Representatives and Democrats dominating the Senate.
If Obama wins, that means he'll face a Republican House that's no more receptive to him than it has been for the past two years. If Romney's the winner, Senate Democrats are sure to treat him with similar hostility.
Indeed, Harry Reid, the Senate majority leader, recently called it "laughable" that Romney was insisting on the campaign trail that Democrats would co-operate with him if elected president.
"Senate Democrats are committed to defending the middle class, and we will do everything in our power to defend them against Mitt Romney's Tea Party agenda," Reid said in a statement.Suggest a correction