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. Romney campaigned there Sunday and was headed back on Election Day. No Republican presidential candidate has carried the state in nearly a quarter century.
—8:30 p.m.: Polls close in Arkansas (six), where Romney is comfortably ahead in surveys.
—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.
— 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.
—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.
— 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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