U.S. President Barack Obama and Republican challenger Mitt Romney have made their final arguments to voters in key political battleground states on the eve of the 2012 presidential campaign.

Mr. Obama made campaign stops Monday in Wisconsin and Ohio, before holding a final rally in Iowa, the state that gave him his first primary victory in his 2008 White House campaign. The Democratic incumbent boasted of his accomplishments during his presidency, including the bailout of the U.S. auto industry and the killing of Osama bin Laden, but said he needed another term to complete his agenda.

Mr. Romney started his day in Florida, Virginia and Ohio, before ending with a rousing late night rally at an arena in New Hampshire, where he launched his campaign more than a year ago. The former Massachusetts governor said his record as both a businessman and politician shows he, and not Mr. Obama, would bring about real change for the nation.

Mr. Romney will vote in his hometown of Boston Tuesday, and has scheduled two last-minute Election Day events in Ohio and Pennsylvania. The president and his wife, Michelle, will spend Tuesday in their home in Chicago.

U.S. political analysts say a handful of the country's 50 states will decide Tuesday's election, with the remainder leaning toward or firmly in the grasp of either the president or Mr. Romney. U.S. presidential elections are not decided by the national popular vote, but rather by an electoral college system in which the importance of each state on the outcome is roughly equivalent to its population.

Millions of voters across the country have already cast ballots under early-voting rules. But the vast majority of the electorate will still head to polling places in schools, firehouses, churches and elsewhere on Tuesday. Voters in the small New Hampshire towns of Dixville Notch and Hart's Location cast their ballots at midnight , keeping with tradition in being the first locations in the nation to vote on Election Day. Mr. Obama and Mr. Romney tied at five votes each in Dixville Notch. In Hart's Location, the president won 23 votes while Mr. Romney finished with nine.

A wide collection of polls shows the two candidates in a very close race nationally. But state-by-state polls show Mr. Obama with steady, but narrow leads in most of the closely contested states likely to determine the outcome.

Along with the race for president, all 435 seats in the U.S. House of Representatives and 33 of the 100 Senate seats are being contested in Tuesday's election. Analysts generally say Republicans will continue to hold their majority in the House, while the president's Democratic party could maintain their slim majority in the Senate.