The US presidential election hinges once again on the economy, according to one exit poll.
The survey conducted for Associated Press showed 6 in 10 voters say the economy is the top issue facing the nation, with unemployment and rising prices hitting voters hard.
About 4 in 10 say they think the nation’s economy is on the mend, but more say that things are getting worse or are bad and stagnating.
About half of voters say the previous president, George W. Bush, shoulders more of the blame for economic challenges than Barack Obama. Just a quarter of those surveyed in the exit poll say they are better off than four years ago.
After billions of dollars spent, more than a million advertisements aired and hundreds of campaign rallies staged, Americans finally went to the polls today to decide who will be the next president of the United States.
President Barack Obama congratulated his Republican rival Mitt Romney today for running a hard-fought race for the White House and expressed confidence he would win re-election during a stop at a local campaign office to thank volunteers.
"I ... want to say to Governor Romney congratulations on a spirited campaign. I know that his supporters are just as engaged and just as enthusiastic and working just as hard today," he said as volunteers made phone calls encouraging supporters to get to the polls.
"We feel confident we've got the votes to win, but it's going to depend ultimately on whether those votes turn out. And so I would encourage everybody on all sides just to make sure that you exercise this precious right that we have that people fought so hard for us to have."
Mr Romney cast his vote in a Boston suburb this morning, saying he felt good about his chances of winning the presidency.
After voting, the former Massachusetts governor kissed his wife Ann goodbye and headed out for last-minute campaigning in Cleveland and Pittsburgh - cities in the crucial electoral states of Ohio and Pennsylvania.
Asked how he felt about his prospects in Ohio, he said, "I feel great about Ohio."
It was the first time Mr Romney has spoken to the traveling media corps since September 28th - a five-week silence.
Later in the morning, Mr Romney's vice presidential running mate Paul Ryan voted with his family in tow at the Hedberg Public Library in his hometown of Janesville, Wisconsin.
Most eve-of-election polls showed Mr Obama with a razor-thin lead over Mr Romney. The winner will be determined by who gets 270 electoral college votes; most polling experts agree Mr Obama has more paths to get there.
A final national NBC/Wall Street Journal poll showed Mr Obama had the support of 48 per cent of likely voters, with Mr Romney on 47 per cent, within the margin of error. Real Clear Politics, which provides an aggregate of published polls, indicated Mr Obama was marginally ahead in all but two battleground states, Florida and North Carolina.
Whichever candidate wins, a razor-thin margin might not bode well for the clear mandate needed to help break the partisan gridlock in Washington.
In a frantic final day of campaigning, both candidates predicted the winner would be determined by which of their operations could get the most supporters to the polls. “This is going to be a turnout election,” Mr Obama said.
At a rally in Virginia, featuring an enormous “Get Out and Vote” banner, Mr Romney said: “We have one job left and that’s getting people out to vote.” In response, the crowd chanted “One more day!”
Both Mr Obama and Mr Romney continued to present themselves as the real agents of change while painting the other as a return to the status quo.
US vice president Joe Biden has cast his vote in the election at a school in Greenville, Delaware, saying “it’s always a kick”.
Mr Biden shook hands with and hugged other voters as he waited. He urged Americans to vote “even if you have to stand in line”.
Both candidates meanwhile sought to benefit from some star power. Mr Romney was joined in New Hampshire by Kid Rock while Mr Obama had rapper Jay-Z with him in Columbus and Bruce Springsteen as his warm-up act.
Under the US system, the winner of the presidential election is not determined by the nationwide popular vote but in state-by-state contests. The candidate who wins a state - with Maine and Nebraska the exceptions - is awarded all of that state’s electoral votes, which are apportioned based on representation in Congress.
In 2008, an estimated 130 million people voted, a turnout of about 55 per cent but that could be down slightly this year.
More than 30 million people have already voted in 34 states, either by post or in person.