Going into this election day, public opinion polls show Virginia, one of the key swing states, is deadlocked. The trends suggest it could be a very long night for the candidates.
Pivotal variables will be partisan enthusiasm and turnout and the role of independents, who broke for President Obama in 2008 but for Gov. McDonnell the next year. Political analyst Dr. Bob Holsworth says even the candidates must think it's close.
"We usually think we have this figured out days before the election, but right now, we really don't," says Holsworth. "Even here in Virginia, what we've seen is that both presidential candidates are here on election eve, on two days before the election."
He says while presidential candidates don't always have coattails, this year they could impact Virginia's U.S. Senate election.
"So much of the vote is likely to follow what happens at the presidential level," says Holsworth. "So the question then becomes: is there going to be crossover, how much, and who's going to benefit?"
Holsworth adds that if the close race ends in a tied electoral college, the House would choose the President and the Senate the Vice President.
"And the delicious irony exists, of course, that you could have a Romney-Biden result," he says.
Another wild card in a close election would be the number of provisional ballots cast, since they won't be counted unless voters provide IDs within just a few days.