Some 120 million Americans go to the polls today after an epic presidential contest with President George W. Bush and his Democratic challenger Senator John Kerry campaigning frantically up to last night to break an apparently deadlocked election.
Several polls published in the last 24 hours all show a statistical dead heat, with neither Mr Bush nor Mr Kerry drawing away. Mr Bush is, however, marginally ahead in most polls, the exception being Fox News which showed the Democrat ahead for the first time, by two points.
The outcome of the election will likely be decided by the ground war fought today in key swing states like Florida, Ohio and Pennsylvania, where tens of thousands of volunteers will mount a huge voter mobilisation drive to get supporters to the polling stations.
Mr Bush wound up his campaign yesterday with a dizzying six-state, seven-stop swing across country before retiring to his ranch in Crawford, Texas, where he will spend polling day.
Mr Kerry started off with a rally in Florida then took off on a last day dash through Wisconsin, Michigan and Ohio, planning to end last night with an open-air "victory" concert in Cleveland Ohio featuring rock star Bruce Springsteen.
The first results of polling will not be known before 11.00 p.m. Eastern Standard Time this evening (4 a.m. in Ireland) and if the election is close a winner might not emerge until later in the week.
As the counts come in from across the 50 states and the District of Columbia tonight and tomorrow, Mr Bush will travel to the White House to await the outcome and Mr Kerry will return to Boston.
After early speculation that the tape released by Osama bin Laden on Friday had benefited Mr Bush because of voter resentment at the al-Qaeda leader mocking their president, it seems the opposite has happened.
A Gallup poll for CNN/USA Today, conducted after the broadcast of the tape, showed Mr Kerry cutting Mr Bush's 22 point lead on terrorism to 11 points and his 14 point lead on Iraq to four points.
Four of the latest polls show a dead heat and six gave Mr Bush a lead of one to three points, with the percentage of undecided voters varying from two to eight points. Democrats were quick to say that undecided votes usually go to the challenger but Republican national chairman Mr Ed Gillespie said last night this was an "old wives' tale" and that Ronald Reagan had got most support from undecided voters when successfully seeking re-election in 1984." Democratic Party chairman Mr Terry McAuliffe said "this is about 270 electoral college votes" and Democrats were ahead in the polls in Ohio and Florida where voter registration has been high.
"You will be shocked by the number of first time voters who come out" to vote for Mr Kerry, he said, pointing out that polls show voters under 30 heavily favour the Massachusetts senator.
Whoever wins today will face the challenge of healing the wounds caused by a sometimes nasty, expensive contest and restoring US prestige in the world damaged by the invasion of Iraq.
Mr Bush hammered home the national security theme that has dominated his campaign, telling reporters at the start of his tour of Ohio, Pennsylvania, Wisconsin, Iowa, New Mexico and Texas: "I want to continue telling the people what I intend to do to protect them. This election comes down to who do you trust. Who do you trust to make this country secure?"
Mr Kerry told crowds at his rallies: "We need a new direction, not more of the same."