With a huge expansion in mail-in voting to safeguard against the Covid-19 pandemic, nearly 100 million people have already made their choice
Polling stations opened in New York, New Jersey and Virginia early Tuesday, marking the start of US Election Day as President Donald Trump seeks to beat forecasts and defeat challenger Joe Biden.
The vote is widely seen as a referendum on Trump and his uniquely brash, bruising presidency that Biden urged Americans to end to restore "our democracy."
With a huge expansion in mail-in voting to safeguard against the Covid-19 pandemic, nearly 100 million people have already made their choice.
Biden has the wind in his sails after indications that Democratic enthusiasm in the early voting may be matching the more visible energy at Trump's impressive rallies.
In one of US history's great political gambles, Biden stuck to socially distanced gatherings with small crowds right up to the last moment, in stunning contrast to Trump's constant, large rallies where few supporters so much as bothered with masks.
But the Democrat, making his third attempt at the presidency, clearly senses that his calmer approach and strict attention to pandemic protocols is what Americans want after four tempestuous years.
In chilly downtown Pittsburgh, Justine Wolff said she had cast her ballot for Biden already and was cautiously hopeful he would carry Pennsylvania, which along with Florida may be the tightest of all the swing states that decide close national elections.
But where many early votes are believed to have been cast by Democrats, Trump's side is hoping for a massive wave of Republican supporters voting in person on Tuesday.
The first polling stations opening were in two New Hampshire villages, Dixville Notch and Millsfield, starting at midnight. Most polling stations on the East Coast were to open at 1100 or 1200 GMT.
A tiny hamlet of 12 residents in the middle of the forest, near the Canadian border, Dixville Notch has traditionally voted "first in the nation" since 1960.
The vote took minutes, as did the count: five votes for Biden, and none for Trump.
Warning of violence
Trump himself is planning to visit his campaign headquarters in Virginia on Tuesday, while Biden will travel to his birthplace of Scranton, the scrappy Pennsylvania town where Trump also visited on Monday.
There are worries that if the election is close, extended legal chaos and perhaps violent unrest could ensue -- not least because Trump has spent months trying to sap public trust in the voting process in a nation already bitterly divided along political fault lines.
He ramped up these warnings in the final days, focusing especially on Pennsylvania's rule allowing absentee ballots received within three days after Tuesday to be counted.
In a tweet flagged with a warning label by Twitter on Monday, he said this would "allow rampant and unchecked cheating."