Early results showed a tight race in US battleground states Tuesday as Joe Biden hopes that a polarised electorate will defeat President Donald Trump in the face of a deadly pandemic.
Preliminary figures showed a deeply divided nation and mixed signs for each candidate, with Biden appearing to underperform in the crucial state of Florida as Trump made inroads in Cuban-American-dominated Miami.
But Biden was also outpacing Trump in suburban areas that have traditionally tilted to the president's Republican Party including around Atlanta in Georgia.
US networks projected winners in several expected states after polls closed, with Biden winning vote-rich Virginia as well as tiny Vermont and Trump triumphing in Indiana, Kentucky and West Virginia.
Historic bellwether Ohio – where, like Georgia, Biden has seen hope after months of polls showing comfortable margins for Trump – was yet to report most results as polling closed at 7.30pm (2330 GMT).
But with more than 100 million Americans voting ahead of Election Day due to the Covid-19 pandemic, definitive results could take hours or even days in the most crucial states such as Pennsylvania.
Trump, 74, expressed confidence as the evening approached, tweeting in all his characteristic all-caps: "WE ARE LOOKING REALLY GOOD ALL OVER THE COUNTRY. THANK YOU!"
In a break with the traditional firewall between campaigns and government, the norm-shattering Trump scrapped an event at his hotel in Washington and was watching results at the White House.
It was not clear whether he would speak to the public at some point but he said earlier Tuesday that he wasn't yet "thinking about a concession speech or acceptance speech."
"Winning is easy," he said. "Losing is never easy – not for me."
Biden, hunkered down with family at home in Delaware, likewise said that voter patterns during the day seemed to favour his side.
"What I'm hearing is that there's overwhelming turnout. And overwhelming turnout particularly of young people, of women, and an overwhelming turnout of African American voters, particularly in Georgia and Florida, over the age of 65," he told reporters.
"The things that are happening bode well for the base that has been supporting me."
Trump has repeatedly refused to confirm he will accept the results of the election – a first for a US president. He argues, without offering proof, that the vast number of mail-in ballots could be used to rig the polls against him.
In the final run-up to Election Day, Trump focused especially on Pennsylvania, which allows ballots postmarked by Election Day to be counted, even if they arrive afterward.
"The whole world is waiting," Trump said early Tuesday.
"You can't have these things delayed for many days," he went on, adding ominously that "a lot of bad things" can happen.
"We should be entitled to know who won on November 3," he said.
However, he somewhat dampened fears that he will try to declare victory prematurely, telling Fox News that he will only declare "when there is victory."
Fears of Covid-19 have driven a huge flow of early voters, encouraged by Biden. Trump has countered by holding dozens of mass election rallies with no social distancing, underlining his message that it's time to move on.
Roughly one-third of the Senate is up for grabs and Republicans risk losing their 53-47 majority.