"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