When will we know who will be the next president?

(CNN) — 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.

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, we’ll start to get some indicators shortly after the first wave of poll closings, at 7 p.m. ET. Battleground states in that group include Virginia, with Ohio following at 7:30 p.m.

Florida and many Midwestern states follow at 8 p.m. ET. West Coast states and Hawaii stop voting at 11 p.m. ET, and the last Americans will cast their ballots, in Alaska, by 1 a.m. ET on Wednesday.

“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,” said CNN chief national correspondent John King.

“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 political reporter Peter Hamby said 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 critical electoral votes, according to Hamby.

If Ohio becomes key to the election, 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.

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 an estimated 200,000 cast in 2008. About 40,000 were later thrown out.

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?

CNN’s Bill Mears contributed to this report.