With President Barack Obama and Republican challenger Mitt Romney locked in an intense battle for the White House, American on Tuesday voted in an election that followed one of the most expensive and negative campaigns, with pundits predicting a wafer-thin win for the incumbent.
Voters from a small township in the battleground New Hampshire State were the first to cast their ballot shortly after midnight when the polling began.
Dixville Notch in New Hampshire has been casting the first ballot of presidential elections since 1960. So far, it has picked seven out of 13 winners.
For the first time ever, the vote was tied in the township, with both Obama, 51, and Romney, 65, receiving five votes each, another indication of the knife's edge separating the two candidates.
Unlike India and in most of the democracies across the world where the entire nation has one time for the opening and closing of polls, the election schedule in the United States, world's largest democracies, varies from State to State.
In US, the President is not chosen by the popular vote, but indirectly through the electoral college, in which states vote based on population, with a candidate needing 270 out of 538 electoral votes to win.
Hours ahead of the today's elections in which over 180 million people were eligible to vote, both the Romney and Obama campaigns, in their speeches and conference calls with reporters, claimed that enthusiasm was on their side.
Though polling centres in the US opened this morning to decide who will sit in the White House for the next four years, over one-third of the voters have already exercised their franchise using the provision of early voting.
According to latest figures complied by the US Election Project of the George Mason University, more than 30.5 million voters had already cast their ballots.
Obama, who cast his vote through early voting along with First Lady Michelle Obama, led from the front as he became the first US President to do so.
The battle for the presidency has narrowed to 10 swing states, as Obama and Romney engaged in last ditch efforts to break into each others' votebanks yesterday.
This election has witnessed the most expensive and one of the most negative campaigns. More than USD 6 billion were spent by the rival camps in a bid to woo Americans, who were still reeling under a sluggish economy and the impact of the superstorm Sandy that slammed the US East Coast last week claiming nearly 100 lives and causing billions of dollars in losses.
Obama preferred to spend the election day in his home town of Chicago, playing basketball with friends and giving a dozen satellite interviews in several battleground States.
His strategy on the final day of campaigning was to cement his last line of defence in the crucial industrial mid west and attempt to pluck away several insurance states from Romney's target list.
Romney, who started as an underdog but grew into a formidable opponent, dashed through the swing states of Iowa and Ohio, trying to break into the Democrat citadels, telling voters that Obama's record, particularly on the economy, did not warrant a return to the White House.
Obama wrapped up his campaign yesterday at a community college in Colorado.
Opinion polls, have suggested a close contest.
The latest Washington Post-ABC tracking poll released yesterday gave Obama (50 per cent) a three point lead over Romney (47%), which is still within the margin of statistical error.
"The poll also finds that Obama remains the favourite, with 55% of voters saying that he will win. By contrast, 35% believe Romney will win while 10% register no opinion," the daily said.
The polls are too close to call, the CNN said, so did other major news networks.