In the first states to finish voting tonight, Mitt Romney and President Obama each scored early wins.
In the inital flurry of early returns, there were no major surprises, as tensions and excitement rose in a race so close it remained a statistical tie in many places.
Based on exit polls and analysis of the vote in so far, Indiana -- went for Obama in 2008 -- is projected to turn red for Romney tonight. Romney will also pick up Kentucky, West Virginia and South Carolina. Obama, based on those same projections, will win in Vermont.
Each candidate picked up a handful of votes, but they remained far from the ultimate goal of 270 needed to win the presidency.
Among the states that have finished voting are Virginia and Ohio, which have been among the most fiercely contested battlegrounds. The winner of Virginia's and Ohio's electoral votes will not be known for hours as the votes are being counted.
Bracing for a long night, Obama today warned that if the race is close, a clear winner in the presidential election may not be determined until Wednesday morning.
"One way or another we're going to have a winner," he told ABC News' Washington, D.C., affiliate WJLA. "If it's close, it may spill into the morning, but I'm pretty confident that we'll end up having a president-elect come Wednesday."
In the final hours of the campaign today, both men did what they felt was necessary to ensure victory.
For the president that meant a traditional game of basketball, a game he has played before every major election that he has won.
The president, who voted early last month, remained in his home state of Illinois today joining old friends and confidants on a basketball court in Chicago following a morning on television satellite interviews to voters in swing states.
Among those on the court were Education Secretary Arne Duncan, Obama's former body man Reggie Love and former Chicago Bulls star Scottie Pippen. Obama's team won by about 20 points.
Obama skipped playing the pre-election game before just one race, the 2008 New Hampshire primary which he subsequently lost. Since then, the game has become a campaign superstition.
The Romney campaign kept stumping until the last minute, holding rallies in Ohio and Pennsylvania.
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Upon arriving in Pittsburgh this afternoon, Romney got off his plane to find an unexpected crowd of people packed into a garage across from the tarmac to greet him.
Romney, visibly moved by the size of the crowd, walked to the fence that separated him from his supporters and stood for several moments with his hand to his heart as the crowd cheered.
"That's when you know you're going to win," Romney told reporters.
Keeping up that enthusiasm, Romney told reporters that he so far only drafted a victory speech, not a concession. He said if he won, he would likely buy a new puppy for the White House.
"If, assuming I win, one of the benefits would be to get another Weimereiner," he said of the potential breed.
Both campaigns toned down the rhetoric now that voting has begun.
In Green Tree, Pa., Romney thanked volunteers and told them that in getting out the vote today they "don't need to be disparaging of the other guy. The president has run a strong campaign, I believe he is a good man and wish him well, and his family well... but it is time for a new direction. It is a time for a better tomorrow."
Obama visited his campaign workers and after thanking them said, "Congratulations to Gov. Romney on a spirited campaign....I know his supporters are just as engaged."
The costliest election in United States history is also one of the closest as voters formed long lines to finally pick their president after a long and divisive campaign.
After spending nearly $1 billion apiece, Romney and the president are today in much the same place they were months ago at the campaign's outset. The president leads his Republican challenger by so small a margin it is statistically insignificant in most places.
The tightness of the race was expressed at midnight, when the first town to open and close its polls, the tiny hamlet of Dixville Notch, N.H., evenly split its vote five to five.
Mitt and Ann Romney cast their ballots this morning about 9 a.m. in Bedford, Mass., where the candidate remarked that he's feeling "very good" about his chances today.
Asked who he voted for, Romney responded, "I think you know."
Romney traveled today to Ohio and Pennsylvania for last-minute campaign stops. Ohio has emerged as a key to a Romney victory.
Asked about his chances in Ohio, Romney said,"I feel great about Ohio."
The Romneys, accompanied by their son Tagg, were greeted by chants of "Romney! Romney!" and a sign that read "Mitt and Ann enjoy your new White House."
Romney also scheduled interviews with radio stations in Ohio and Virginia.
The fate of the election will rest on the outcomes in a few hard-fought swing states – Florida, Virginia, New Hampshire, Wisconsin, Pennsylvania and most crucially Ohio.
Victory or defeat may very well come down to Ohio, a battleground whose 18 electoral votes may be as critical this year as Florida was in 2000. Both candidates know it, and have spent more time there than anywhere else.
Ohio, or possibly Wisconsin, where Romney has trailed for months, create "a very narrow path to electoral college victory," said Matthew Dowd and Republican strategist and ABC News consultant.
He said the first key state where polls will close is Virginia and a defeat or victory there for Romney could be crucial to the rest of his night.
Obama Plays Basketball as Romney Works Ohio Crowd
"I think Virginia is going to tell us a lot. It's going to tell us if this night ends early for Mitt Romney or if we're in for a long night," Dowd said.
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There are also a few critical demographic groups to watch, including Latinos, young people and women.
Both campaigns have battled for the women's vote, but Donna Brazille, a Democratic strategist and ABC News consultant, said Obama has an advantage with women.
"One thing to remember is that in the last six elections, Democrats are six and zero. We've won the women's vote in every election. That's what makes Democrats competitive," said Brazille.
The final weeks of the campaign proved more exciting than any over the course of the past year and a half. After leading for months, Obama found himself trailing Romney for the first time following a lackluster performance in the first debate in Denver, Co., last month.
But Romney's momentum appeared to have been blunted last week by superstorm Sandy, whose devastation knocked election coverage off the front page and seemed to tilt the race back in Obama's favor.
ABCNews' Emily Friedman contributed to this report