The president appears to have the narrowest of leads over rival Mitt Romney in a number of critical swing states.
However, if victory walks its way to the incumbent president, an uncertain and thorny four years could be awaiting him.
Indications are that under such possible outcome of a slim victory, making him to cling to power, losing the popular vote to Republican Mitt Romney, he stands to tread through a thorny road as he is settled for another four years.
Never before in American history has a sitting president won a second term without winning the popular vote.
This year, it’s within the realm of possibility. A very tight race seems to favor Obama in the most competitive states that will decide the winner, even if growing Republican enthusiasm means more voters overall go for Romney.
If that happens, Obama would face mounting problems – stubbornly high unemployment, Mideast unrest, the “fiscal cliff” of tax increases and spending cuts in January – with little ability to claim Americans support his way forward, political analysts say.
“If there’s any room in these results for Republicans to say the public doesn’t support what he’s doing, it would make an already toxic, incredibly difficult situation that much worse,” Princeton University historian Julian Zelizer said.
The Republican candidate will continue campaigning on election day, as he visits Cleveland in Ohio, and Pittsburgh in Pennsylvania.
Mr Obama will spend the day in his home-town of Chicago. He has recorded a number of television and radio interviews which will air today.
In a possible sign of a tight race ahead, the first voting on election day saw both candidates receive five votes each in the tiny town of Dixville Notch, New Hampshire.
The president wrapped up his campaign with a rally in Iowa, the state where his 2008 campaign sparked into life, and he called on Americans to give him a second chance.
“I came back to ask you to help us finish what we started because this is where our movement for change began, right here,” he said.
“After all we’ve fought through together, we cannot give up on change now. We know what real change looks like.”
The two candidates have criss-crossed a handful of swing states in recent days as they try to energise supporters and secure every last vote. Both have sounded weary and hoarse at times.
The latest ‘poll of polls’ by RealClearPolitics puts Mr Obama on 48.8% and Mr Romney on 48.1%.
In swing states, Mr Obama has a three-percentage point lead in Ohio and was ahead by slimmer margins in Virginia and Colorado. Mr Romney led in Florida.
The other states to watch include Iowa, Wisconsin, Nevada and Pennsylvania, where Mr Romney has poured money into a late run.
Barack Obama’s final rally in Iowa
The electoral college system and the way the state polls are going suggests that Mr Obama could be headed toward re-election partly due to his lead in Ohio, according to Ipsos pollster Julia Clark.
A victory in US presidential elections relies not on a popular vote count but reaching 270 electoral college votes. They are allocated to each state based on population size.
Ms Clark said: “Obama only needs a couple of these swing states and the data suggests that he’ll win one or two of them.”
Mr Romney’s advisers dismiss those polls and believe they have the momentum.
-SkyNews and Times of India