When will we know results of presidential race?

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It’s been a grueling campaign. You just want to sit down with a bowl of popcorn and find out who will be president for the next four years.

So when will we know?

Technically speaking – who the heck can say?

With a race that went into Election Day neck and neck, and plenty of questions about how key battleground states will play out, it’s reasonable to assume a long night is in store.

What to watch for

It could be even longer if the election ends up balanced on the edge of a razor-thin vote in Ohio or if voting irregularities spark legal challenges in any of a number of critical states.

Either situation could drag out the decision until mid-November or even longer, analysts say.

Whatever happens, some indications should begin to trickle in now that the first waves of poll closings have come, ending voting in Virginia, Florida, Ohio and other key states.

West Coast states and Hawaii will stop voting at 11 p.m. ET, and the last Americans will cast their ballots in Alaska by 1 a.m. ET Wednesday.

The first place to look: Virginia, according to analysts. But the reporting of results was paused after 7 p.m. because many voters remained in line after the scheduled poll closing time, the state Board of Elections said.

When results do come in, Prince William County will be a key indicator, CNN chief national correspondent John King said.

“One of the first things I’ll look at are the margins in the northern Virginia suburbs closest to Washington, D.C., especially Prince William County,” he said.

Drama awaits in battleground states

“If Gov. Romney is ahead or at least in play there, it means Virginia is in play, and we could have a long, competitive night,” King said. “If he’s not in play, it could be over before we even get to the Central time zone.”

CNN’s chief politcal analyst, Gloria Borger, agreed that Virginia will have a lot to say about what happens later.

“We have to look at Loudoun County in Virginia, and if the president were to win Virginia, obviously, the path to 270 is a lot easier for him,” she said. “But if Mitt Romney wins Virginia, it could be a much longer night.”

CNN political reporter Peter Hamby said that results from early and absentee balloting in Pasco County, Florida, could also offer a tantalizing glimpse of what the night may hold.

Barack Obama won the early and absentee vote in the slightly Republican-leaning county in 2008. If Obama comes up trailing when those early votes are posted soon after polls close, it could indicate the president might have trouble carrying Florida and its crucial electoral votes, according to Hamby.

Frum: U.S. voting system is a disgrace

If Ohio becomes key to the election, it’s possible that bag of popcorn isn’t going to hold you.

If the margin separating Romney and Obama is particularly thin, the election in that key battleground state could ride on absentee and provisional ballots. And that could keep the nation in suspense for a whopping 10 days.

Ohio provisional ballots hold key

That’s how long Ohio law gives poll workers to check the eligibility of provisional voters.

Ohio has one of the nation’s highest rates of provisional voting, with 211,000 cast in 2008, according to Ohio Secretary of State Jon Husted. About 40,000 were later thrown out.

Husted says he thinks the election in Ohio will hinge on the state’s central counties, and the results will be known before midnight.

“I really believe that we will be able to project a winner tonight,” he said. “I think that people will have to stay up past their bedtime to be able to do that. But it’s likely that we’ll know by the end of the evening.”

Popular-electoral split is possible

The worst nightmare scenario is a redux of 2000, when the nation suffered through weeks of uncertainty amid recounts and legal challenges surrounding the vote in Florida.

And, sorry to say it, as tightly contested as this race is, it is a possibility, analysts say.

“Between provisional balloting, absentee balloting and voting technology, I think there are untold different ways that this is a tense, contested election,” said Rebecca Green, co-director of the Election Law Program at William & Mary Law School. “It’s pretty certain there’s going to be some litigation when this is over on November 6.”

As we said – who knows?

Election 2012: Projections

CNN’s Bill Mears contributed to this report.