10 p.m.

Election Night: Hour-by-Hour Guide

Polls close in four states, including the last of the battlegrounds, Iowa (six) and Nevada (six).

Iowa's been leaning toward Obama, but watch how the vote breaks down geographically. Can Romney's advantage in GOP-heavy western Iowa overcome Obama's edge in eastern swing territory?

If Obama wins Ohio and Wisconsin, Romney would have to have help from the West, in places like Nevada and Colorado. Nevada, where two-thirds of the electorate votes early, has been moving Obama's direction in recent weeks, powered by strength in huge labor and Hispanic voting blocs. A Romney incursion there would really mean something.

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What to Watch on... Stock up on munchies and make sure the batteries in your TV remote are fresh. With this year's presidential election razor-close to the finish, Tuesday could be a long night.

Even if the presidency isn't decided until after midnight EST, there will be plenty of clues early in the evening on how things are going for President Barack Obama and Republican Mitt Romney. Obama has more options for piecing together the 270 electoral votes needed for victory, so any early setbacks for Romney could be important portents of how the night will end.

Here's a timetable for armchair election watchers on how the night will unfold, based on what time the last polls close in each state. All times are EST. Stock up on munchies and make sure the batteries in your TV remote are fresh. With this year's presidential election razor-close to the finish, Tuesday could be a long night.

Even if the presidency isn't decided until after midnight EST, there will be plenty of clues early in the evening on how things are going for President Barack Obama and Republican Mitt Romney. Obama has more options for piecing together the 270 electoral votes needed for victory, so any early setbacks for Romney could be important portents of how the night will end.

Here's a timetable for armchair election watchers on how the night will unfold, based on what time the last polls close in each state. All times are EST. Here are five things to watch for in the final week of the presidential race between President Barack Obama and Republican nominee Mitt Romney:

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7 p.m. Polls close in six states but all eyes will be on Virginia, the first of the battleground states to begin reporting results. If either candidate is comfortably ahead in Virginia, with 13 electoral votes, that could be a leading indicator of which way the night is going.

Virginia typically has been fairly fast at counting ballots. But there's a new voter ID law in the state that could complicate things this year. Voters who don't bring identification to the polls still can have their ballots counted if they produce ID by Friday. If the race in Virginia is super tight, it could come down to those provisional ballots. On Election Night, no one will even know how many of them are out there.

Virginia is especially important for Romney. In 2008, Obama became the first Democratic presidential candidate to carry Virginia since 1964. Keep an eye on turnout in northern Virginia's Democratic strongholds for an early idea of which way the state will go.

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7:30 p.m. Polls close in three states, including all-important Ohio (18 electoral votes) and competitive North Carolina (15).

If Ohio is particularly close, and polls suggest it might be, there's a chance the outcome there won't be known until after Election Day, and the presidency could hinge on it. In the last several elections, between 2 percent and 3 percent of the state's votes came from provisional ballots, which aren't counted until later. In 2004, after a long, tense night counting votes, the presidential race wasn't decided until 11 a.m. the next day, when Democrat John Kerry called President George Bush to concede Ohio and the presidency.

Romney desperately needs Ohio; no Republican has won the presidency without it. Without Ohio, Romney would need victories in nearly all the remaining up-for-grabs states and he'd have to pick off key states now leaning Obama's way, such as Wisconsin and Iowa. Obama has more work-arounds than Romney if he can't claim Ohio.

In North Carolina, the most conservative of the hotly contested states, Romney appeared to have the late edge in polling. Obama, who narrowly won the state in 2008, has paid less attention to it recently. An Obama victory there could point to broader troubles for Romney.

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8 p.m. More pieces of the puzzle will start falling into place as polls close in the District of Columbia and 16 states, including battlegrounds Florida (29) and New Hampshire (four).

Democratic-leaning parts of Florida tend to be the last places to report, so be careful about jumping to a conclusion if Romney looks strong early on. Most of the polls in Florida close at 7 p.m. Eastern, so by 8 p.m. Eastern, when the last polls close, results will start to roll out quickly. But fully 4.5 percent of votes in Florida weren't counted on election night in 2008, so if things are tight, no one's going to be hasty about declaring a victor in the state. Especially after the 2000 fiasco in which the winner in Florida, and thus the presidency, wasn't determined for more than a month. If you want to get really granular, Hillsborough County, home to Tampa, is widely considered a bellwether for the state.

Tiny New Hampshire is another competitive state to watch closely.

Also keep watch on Pennsylvania for any signs of a Romney surprise. The state has long been considered safe for Obama, but Republicans started running ads there in the final week of the campaign and the GOP ticket was campaigning there Sunday. No Republican presidential candidate has carried the state in nearly a quarter century.

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8:30 p.m. Polls close in Arkansas (six), where Romney is comfortably ahead in surveys.

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9 p.m. Polls close in 14 states, including battlegrounds Colorado (nine) and Wisconsin (10). Democrats have carried Wisconsin for six straight presidential elections and Obama had the edge in polling going in, so a flip here would be especially noteworthy.

Colorado, where almost 80 percent of voters cast early ballots, could be a straggler because it's so close. Historically, as much as 10 percent of the state's vote doesn't get counted on election night, and those ballots could be decisive in a close race.

Information from exit polls could help flesh out the Colorado picture: Young professionals and Hispanic voters were central to Obama's victory there in 2008, but the sluggish economy has hurt his standing.

Two more to watch: Minnesota and Michigan. The states long have been considered safe for Obama, but the Republicans made late moves there.

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10 p.m. Polls close in four states, including the last of the battlegrounds, Iowa (six) and Nevada (six).

Iowa's been leaning toward Obama, but watch how the vote breaks down geographically. Can Romney's advantage in GOP-heavy western Iowa overcome Obama's edge in eastern swing territory?

If Obama wins Ohio and Wisconsin, Romney would have to have help from the West, in places like Nevada and Colorado. Nevada, where two-thirds of the electorate votes early, has been moving Obama's direction in recent weeks, powered by strength in huge labor and Hispanic voting blocs. A Romney incursion there would really mean something.

(AP Photo)

Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
11 p.m. Polls close in five western states, but most are foregone conclusions for Obama. He gets 78 electoral votes from California, Hawaii, Oregon and Washington; Romney gets four from Idaho.

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1 a.m. Wednesday The last of the polls close, in Alaska. Romney gets three electoral votes. Will many people still be up?

Political junkies could well be waiting to see how things play out in one or more battleground states.

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