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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