They were queuing at some polling stations at 4.30am, with voters waiting hours to cast their ballots. Polling watchdogs are reporting some irregularities in key states: a sign of trouble to come?
If the early queues outside polling stations across America are anything to go by then it is set to be a record turnout. In some of the key battleground states where the campaigns have invested everything they have into getting out the vote, there are tales of lines forming by 4.30am.
In Virginia, one of the most hotly contested states, officials said there had been huge numbers of voters turning out, some waiting patiently for more than an hour to cast their ballot.
In south Florida the wait has been far longer: polling stations were inundated with huge queues of early voters over the weekend, and it looks like the same there today.
Even in Massachusetts, hardly a close run state, numbers have been off the scale.
Election observers and legal campaigners say they are keeping track of voting irregularities, from malfunctioning electronic voting machines to issues with new voter ID laws.
The former Vermont governor Howard Dean told NBC that voters in Pennsylvania had been told they would not be allowed to vote unless they could produce a valid ID, which is not the case. He said a judge had tried to put a stop to it, to no avail.
In storm-ravaged New York and New Jersey, there was a scramble to try to re-open polling stations in buildings damaged by the weather, but many still lacked any power supplies this morning, or were simply too badly damaged.
Both states are allowing people who were forced to move out of their homes because of the storm to vote anywhere that is convenient, but there have been some technical glitches with efforts to let New Jersey residents vote by email. Some voters claim the computers have crashed when they tried to send their ballots back.
The Denver Post has reports from Colorado of people turned away because they were not on the registration list, with others turning away because they were put off by the long lines.
Whatever happens, you can be sure that lawyers from both sides are already on the case: Romney advance staffers are already on standby to remain in swing states, ready to launch court proceedings if there is a recount. Team Obama has lawyers at each polling location in Virginia, and possibly other states too.
Just watch out for the number of provisional ballots in Ohio. Those are the voting sheets which people are given if there is some question over whether they are entitled to vote.
Top Obama aide David Axelrod told CNN: "We are going to watch those ballots closely", and you can bet the Republicans will be doing the same. Trouble is, Ohio's complicated election law means those ballots would not even be counted for ten days, to give people a chance to prove their voting credentials.
The New Yorker warns that if it the result was close enough to force to that kind of recount, no-one knows how the procedure would actually work. Let us hope the result is clear enough tonight: the thought of this election turning into a 2000-style legal nightmare would surely be too much to bear.
Felicity Spector writes about US politics for Channel 4 News