For his part, Romney called Obama's record one of underachievement and failure, telling a cheering Virginia crowd at his second stop of the day that "almost every measure he took hurt the economy, hurt fellow Americans."
At an earlier event in Florida, Romney asked if people wanted four more years like the last four, raising the specter of continuing gridlock in Washington and adding that "unless we change course, we may be looking at another recession."
He promised to repeal the health care and Wall Street reforms of the Obama presidency and to "limit government rather than limiting the dreams" of Americans.
"We have known many long days and some short nights and now we are close. The door to a brighter future is open. It is waiting for us. I need your vote. I need your help. Walk with me. Tomorrow we begin a new tomorrow," Romney said.
It takes 270 of the 538 total electoral votes to win the presidency.
While both campaigns sought to project confidence in victory, the possibility loomed that neither candidate will get more than 50% of total votes cast. In a less likely but mathematically possible result, a tie in the Electoral College could occur, which would set up a congressional vote to break the deadlock.
As the challenger, Romney sought to frame the election as a referendum on Obama's presidency and to capitalize on his own background as multimillionaire businessman by depicting himself as better able to handle economic issues identified by voters as their biggest concern. His campaign stump speech hammered Obama over high unemployment and what he called excessive taxes and regulations that Romney said stifled faster growth.
Obama and his team attacked Romney's politics and his background as a venture capitalist, saying he would back policies favoring the wealthy over the middle class and exacerbate the already widening income and opportunity disparity in the country. The president wanted the race to come down to competing visions for the future and his oft-repeated goal of restoring the promise of the American dream of equal opportunity for all.
In particular, Obama repeatedly noted he backed a taxpayer bailout that helped restore General Motors and Chrysler while Romney opposed it. The issue resonated in auto industry states like Michigan and Ohio, which was considered the most significant of the battlegrounds in the final days of the race.
Aside from the policy differences, the election amounted to a campaign chess match targeting specific states and demographic groups as part of plan to create a path to 270 electoral votes. Polling portrayed a race that hinged on the social and democratic divides in American society, with Obama supported most strongly by women, minorities and young respondents, while Romney did better among wealthy and middle class white men, from senior citizens down to 30- year-olds.
In response, Obama emphasized the anti-choice positions of Romney and conservatives on abortion, their stance against gay rights and their opposition to providing a path to legal status for undocumented immigrants.
Re-election offered Obama, 51, the chance to secure a two-term legacy and seek further reforms he promised in his historic campaign of 2008 but was unable to deliver in the first four years. In particular, he has made comprehensive immigration reform a top target, as well as a deficit reduction plan that ends tax breaks for income over $250,000.
However, the wave of optimism that carried to him to victory in 2008 seemed muted four years later, with former supporters angered by the failure to achieve the kind of change in Washington they believed Obama had promised but failed to deliver.
Particular issues of discontent included Obama's expanded use of unmanned drones to attack terrorist targets abroad, the lack of broad immigration reform and the continued existence of the federal Defense of Marriage Act that defines marriage as between a man and a woman.
For Romney, a multimillionaire businessman seeking to become the nation's first Mormon president, the election concluded a six-year quest for the presidency to achieve the office that his father -- former Michigan Gov. George Romney -- briefly and unsuccessfully sought in 1968.
Mitt Romney also failed in his first bid for the Republican nomination in 2008, then spent the next two years preparing for a second run that began in 2011 with a grueling primary campaign featuring a record 20 debates.
A former governor of Massachusetts, he shifted to the right for the primary race to overcome a broad field that included former House Speaker Newt Gingrich, former Pennsylvania Sen. Rick Santorum, Rep. Michele Bachmann of Minnesota, Texas Gov. Rick Perry, former U.S. Ambassador to China Jon Huntsman and businessman Herman Cain.
Romney, 65, declared himself "severely" conservative and adopted stances against abortion, gay marriage and a path to legal residency for undocumented immigrants while also opposing higher tax rates as part of a deficit reduction plan. His support remained steady -- though well below a majority -- throughout the primary campaign while opponents dropped out one by one until Romney emerged as the winner and claimed the nomination at the GOP convention in late August.
However, his campaign endured a tough September, due in part to some unforced errors. A secretly recorded video from a May fundraiser became public, showing Romney referring to 47% of the country as dependent on government handouts and therefore unreachable to him as a candidate.
When U.S. diplomatic compounds came under attack on September 11, including an assault that killed the U.S. ambassador and three other Americans in Benghazi, Libya, Romney quickly issued a statement that was criticized for mistaken information and seeking to politicize a sensitive national security issue.
Then, in the first presidential debate on October 3, Romney began an energetic shift back to the political center and scored a clear victory over Obama by presenting himself as more moderate than the right-wing zealot portrayed by the president.
He acknowledged the need for government regulation, opposed deporting undocumented immigrants and generally backed Obama's positions on the war in Afghanistan, the conflict in Syria and other foreign policy matters.
Obama's lackluster showing in the first debate contributed to an overwhelming consensus among analysts and poll results that Romney carried the night, and he began rising in the polls to erase what had been a consistent Obama lead since the conventions a month earlier.
Stronger performances by Obama in the second and third debates began to slow Romney's momentum, though the Romney team claimed a surge put states like Michigan and Pennsylvania back in play. They were previously thought safe for the president.
With polls tightening in the final weeks, Romney or his surrogates heightened their attacks on key issues, including a campaign ad that implied the auto bailout led to shifting the production of iconic Chrysler Jeeps to China. The automaker joined the Obama campaign in complaining that the ad was misleading, and the president said it was intended to scare workers for political gain.