Americans have started voting in an election which amounts to a referendum on Donald Trump and his presidency, which has seen more anger and division than since the Vietnam War era of the 1970s. Many fear that Trump could dispute the results, increasing the tension.
Donald Trump was characteristically defiant to the end of his campaign with crowded rallies in four states on Monday, where he repeated his unprecedented claims for a US president that the polls risk being rigged against him.
After almost non-stop speeches in a final three-day sprint, he ended up in the early hours of Tuesday in the industrial town of Grand Rapids, Michigan -- the same place where he concluded his epic against-the-odds campaign in 2016 where he defeated apparent frontrunner Hillary Clinton.
"We are going to gain four more years in this very beautiful White House. We wrote a page of history four years ago, and tomorrow we will once again write a page of history," the 74 year-old Trump told an adoring crowd of thousands, some of whom had been waiting since early Monday morning.
Democratic opponent and frontrunner Joe Biden held his final rally in Pittsburgh, Pennsylvania on Monday night, a vital electoral battleground.
Now on his third candidacy, the veteran politician urged supporters to end the Trump presidency.
"It's time to stand up and take back our democracy," Biden said, where he was joined by pop superstar Lady Gaga.
Biden has a slight lead in the pivotal state, which Trump won by less than a percentage point in 2016.
But the polls have tightened in recent days, and after the billionaire's shock victory four years ago, some Democrats are nervous.
Biden, 77, leads in almost every opinion poll, buoyed by his consistent message that America needs to restore its "soul" and get new leadership in the midst of a coronavirus pandemic that has killed more than 231,000 people.
Barricades in preparation
The tension in the air is also palpable, with shop-owners in dozens of cities across the country – including Washington D.C - preparing for the worst on election night, some going as far as to barricade their store windows.
According to a report by the NGO Crisis Group, the risk of post-electoral violence is high.
"It’s a country which is very divided," director Robert Malley told RFI’s Washington correspondent Anne Corpet.
"There were the violent demonstrations after the murder of George Floyd, and the country is already on edge. We’ve had some very difficult years, with permanent tension during the Trump presidency."
"He’s only adding fuel to the fire by saying for example that fraud would be the only way he could lose the election."
Well armed right-wing groups
Malley says the tension is underlined by the rise of extreme right-wing, white supremacist groups, who are very well armed. These groups have been underestimated by national security in recent years he says.
He also points to the presence of radical left-wing groups which have used violence during the recent protests.
While Tuesday is formally Election Day, in reality Americans have been voting for weeks.
With a huge expansion in mail-in voting to safeguard against the Covid-19 pandemic, nearly 100 million people have already made their choice.
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 opened at 6:00 am or 7:00 am (1100 or 1200 GMT), followed gradually by the rest of the country.
Trump himself is planning to visit his campaign headquarters in Virginia on Tuesday, while Biden will travel to his birthplace of Scranton, the modest Pennsylvania town where Trump also visited on Monday.