What happens if US presidential election ends in a tie?

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The race to the White House remains close ahead of the US presidential election on Tuesday, with national polls showing US President Barack Obama and Republican challenger Mitt Romney in a statistical tie.

But after all the votes are tallied, what happens if the election ends in an actual tie?

"I would put this in the category of a possibility, not a probability," Peter Bergerson, a political science professor at Florida Gulf Coast University, told the Florida newspaper The News-Press.

"This appears to be the closest race in a long time for the possibility of there being a tie."

The US presidential election is not decided by the popular vote. Instead, each state gets a predetermined number of the 538 total electoral votes nationwide, and a candidate must capture 270 electoral votes to win the presidency.

And while a 269-269 tie in the Electoral College is highly unlikely, experts say it could happen.

In one possible scenario, Romney could win tightly contested races in the states of Iowa, Florida, New Hampshire, North Carolina, and Ohio - a feasible achievement based on recent polling data. If Obama were to win Colorado, Virginia, and Wisconsin in this scenario, the contest could plausibly end in an Electoral College deadlock.

Should such an unlikely impasse occur, the US Constitution empowers the House of Representatives to elect the president and the Senate to choose the vice president.

Republicans are expected to maintain their current majority in the House after Tuesday's election, while the Democrats are widely predicted to hold on to their Senate majority.

Assuming each of these chambers of the US Congress votes along party lines, America could be looking at a divided administration, with Romney as the new commander-in-chief and current Vice President Joe Biden staying on as the No. 2 man in the White House.

The last time the US faced such a peculiar presidential end game was in 1824, when no candidate was able to secure a majority of the Electoral College votes. In that race, the House elected John Quincy Adams as president over Andrew Jackson, despite the fact that Jackson garnered more electoral votes.

But those hoping for a similar stalemate this year might be in for a disappointment.

Statistician Nate Silver, who runs The New York Times blog Five Thirty Eight and correctly predicted the outcome of 49 out of 50 states in the 2008 race, has put the chance of a tie in Tuesday's presidential election at just 0.03 percent.