As first polls close, the counting begins in 2012 presidential race

As voters drift out of polling stations Tuesday night, America will get a little closer to knowing whether Mitt Romney or President Barack Obama will be in the White House come January. After countless stump speeches, three debates and historic levels of advertising—it's estimated that $2.6 billion was spent in the presidential race—tens of millions of Americans, some of whom had to stand in line for hours, are casting their ballots. Tonight's winner will most likely inherit at least one crucial Supreme Court nomination, plus messy Congressional negotiations about whether to let the Bush tax cuts expire, and an unpopular 10-year war in Afghanistan. So, when will we know who won? The earliest polls close is at 6 p.m. ET in Indiana, with five more states shutting their polling stations at 7 p.m. At the earliest, the race would be called at 11 p.m., when the West Coast polling stations close and elections officials will have had time to tabulate ballots in other states. But if the race ends up extremely close in a few states, it could take days, or even weeks, to declare a winner. A shrinking electoral battleground this year means that only 11 states are really seen as in play, and their results are the ones political junkies—and the campaigns—will anxiously be awaiting. Though national polls show the two candidates in a dead heat, Obama leads in most of these battleground states' recent polls. The president could get to 270 electoral vote—which is the number need to win—by taking only four battleground states: Wisconsin, Nevada, Pennsylvania and Ohio. Romney needs at least five of the states, including Ohio, to get to victory. Additionally, the swing states of Virginia and Florida, which finish voting at 7 p.m. ET, are seen as must wins for Romney if he is to garner 270 votes. Another state crucial to both Obama and Romney's path to victory, Ohio, closes its polls down just half an hour later, at 7:30 p.m. ET. The Buckeye State tends to vote a bit more Republican than the nation as a whole, but polling there suggests that Obama has been able to reverse that trend and hold an edge there over Romney, perhaps due to the president's support of the auto bailout three years ago. But some have suggested the state polling in Ohio has underestimated Republican voters' enthusiasm and overestimated turnout among groups that tend to vote Democratic. By 8 p.m. ET, the polls will have closed in nine of the 11 swing states. Colorado's and Nevada's polls close at 10 p.m. and 11 p.m., respectively. Both campaigns demonstrated how important Ohio was to their campaigns on Tuesday. Romney and his running mate Paul Ryan spent Tuesday campaigning in the Cleveland area, while Vice President Joe Biden made an unannounced trip to the state to make a last-minute appeal to its voters.