MADISON, Wisconsin - Barack Obama and Mitt Romney made last-ditch appeals to American voters on Monday as campaigning drew to a close with the president holding a slender advantage going into election day.
On the eve of Tuesday's vote, after a see-sawing 18-month battle, Romney was tied with Obama in national polls but the Democrat held narrow leads in ten of the 12 key swing states that will decide who wins the White House.
Both candidates had engaged in a weekend campaign marathon, going deep into the night Sunday in a frenetic 11th-hour search for votes before getting a few hours sleep and starting all over again.
Then Romney was first out of the gate on Monday morning, addressing a rally in the biggest swing state of all, Florida, barely 10 hours after wrapping up an event the night before in Virginia.
"We need every single vote in Florida," Romney told a modest crowd at an airport hangar in Sanford outside Orlando, part of Florida's critically important "I-4 corridor," a string of communities cutting across the state.
"We ask you to stay at it all the way to victory on Tuesday night," the Republican challenger said, calling on supporters to make last-ditch phone calls and door knocks as they chanted back: "One more day! One more day!"
Obama beginning his final day of campaigning in Madison, Wisconsin, told the crowd that Romney was nothing but a "good salesman" and that he, the president, was the only candidate who would bring real change.
"You have seen the scars on me to prove it. You've seen the gray hair on my head to show you what it means for fight for change, and you have been there with me," he said.
Rock legend Bruce Springsteen took the stage before the president and gave a rousing speech dotted with acoustic guitar riffs.
"This election, it's sealed because of this song, right here. Swing states, this is the tipping point," he said.
After the performance, which included hits like "The Promised Land" and "Land of Hope and Dreams," Obama came on stage and the two men bear-hugged.
"I cannot imagine not being fired up after listening to Bruce Springsteen," Obama said to loud applause. "And I can't thank him enough for everything that he's done for this campaign.
"He is an American treasure. And I get to fly around with him on the last day that I will ever campaign. So that's not a bad way to end things."
After taking Springsteen with him to rallies in Ohio and Iowa, Obama returns to his hometown Chicago, where he hopes to celebrate on Tuesday night becoming only the second Democrat since World War II to win a second term.
As the clock ticked down to Tuesday's vote, Romney's efforts included a surprise foray on Monday night into Pennsylvania, a Democratic-leaning state that Republican strategists say is breaking his way.
"We're taking back the White House because we're going to win Pennsylvania," Romney told a crowd of up to 30,000, according to US Secret Service estimates quoted by the campaign, who had gathered on a farm in frigid weather.
Obama advisers dismissed the trip as a sign of desperation from the challenger less than 48 hours from election day.
And yet a valuable character witness, former president Bill Clinton -- the only other two-term Democrat -- will headline four rallies for Obama on Monday in Pennsylvania, to counter Romney's late push there.
Democrats said they were confident of Obama's small but steady lead in key swing states, but acknowledged that everything now depends on getting out the vote.
After Florida, Romney held the first of two Virginia rallies before heading to potential kingmaker Ohio. He then returns to where he launched his campaign 18 months ago: New Hampshire.
US media reported that Romney was considering an unexpected campaign trip to Ohio on polling day itself and the candidate's did nothing to knock back the reports.
"We'll advise a schedule and until then we don't have anything," senior aide Kevin Madden said.
Obama aides have pointed at early voting advantages in Ohio and Florida as evidence that the president is close to sealing the deal but the race is still extremely tight and Romney's camp also appeared confident of victory.
Three separate national polls of likely voters showed the race tied. Only one Pew poll found the president ahead, 48 percent to 45 percent.
But, crucially, Obama is up in 10 of the 12 key swing states and Romney only in two, according to RealClearPolitics, a website that aggregates all the polling.
Eight battleground races are within a three percentage point margin, meaning there is still everything to play for.
Florida, famous for the presidential election debacle 12 years ago which required the hand-counting of thousands of ballots, faced some new election-related problems ahead of Tuesday's vote.
The state's Democratic Party filed a federal lawsuit Sunday over long delays encountered by some voters who were unable to cast votes in southern Florida despite spending hours in line.
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