Obama and Romney are making one final push through several so-called "battleground" states, where the race between the two candidates remains close. Both delivered final arguments for their respective candidacies Monday in Florida, where early voting over the weekend was marred by long lines and a bomb threat at an Orlando-area polling station.
The candidates were scheduled to hold campaign events less than 10 miles apart Monday evening in the strategically important battleground state of Ohio, whose 18 electoral votes are seen as potentially crucial in determining the winner of the election.
Obama carries a slight lead in the polls nationally, according to the website RealClearPolitics, which tracks and averages nationwide polling data. Meanwhile, The New York Times' blog Five Thirty Eight, which analyzes state-by-state polling data, gave Obama an 86.3 chance of winning the presidency as of Monday compared to 13.7 percent for Romney.
Predictably, both campaigns are delivering an optimistic forecast for Tuesday's election.
"The people of America understand we're taking back the White House," Romney told the crowd Monday at an event in Pennsylvania.
The boss' chair in the White House's Oval Office isn't the only one up for grabs Tuesday. Americans will also vote in races for all 435 seats in the House of Representatives, the lower house of Congress where Republicans currently enjoy a 240-190 majority over the Democrats. Five seats are currently vacant.
Republicans are expected to hold on to their House majority, while Democrats are widely predicted to maintain their Senate majority after the dust settles in races for 33 of the upper chamber's 100 seats. Democrats currently hold a 53-47 majority in the Senate.
Election Day also features ballot measures in several states on a range of contentious and divisive social issues in the US.
Voters in Maine, Maryland, and Washington will decide whether to make their states the first in the union to legalize same-sex marriage through direct, popular vote. The initiatives come as the US Supreme Court is expected to issue a ruling in the coming months on the constitutionality of the Defense of Marriage Act, a federal law defining marriage as strictly between a man and a woman.
Voters in Colorado, Oregon, and Washington will also vote Tuesday on whether to legalize marijuana in their states. Proponents of the ballot measures say legalization would bring much-needed revenues from taxes on marijuana while helping to defang criminals trafficking the drug in an unregulated black market.
Should the states decide to legalize marijuana, however, they could find themselves at odds with a federal law banning the sale, possession, and distribution of the drug. The US Justice Department issued an advisory ahead of a similar California ballot initiative in 2010 saying that it would enforce federal drug laws regardless of state laws allowing legal marijuana.
Californians ultimately rejected the ballot measure to legalize the drug in the state.