The knife-edge US presidential race tilted toward Democrat Joe Biden early Thursday, with wins in Michigan and Wisconsin bringing him close to a majority, but President Donald Trump claimed he was being cheated and went to court to try and stop vote counting.
Tallying of votes continued through a second night in the remaining battleground states where huge turnout and a mountain of mail-in ballots sent by voters trying to avoid exposure to the coronavirus made the job all the harder.
Both men still had paths to winning the White House by hitting the magic majority threshold of 270 of the electoral votes awarded to whichever candidate wins the popular vote in a given state.
But momentum moved to Biden, who made a televised speech from his hometown of Wilmington, Delaware to say that "when the count is finished, we believe we will be the winners."
By flipping the northern battlegrounds of Michigan and Wisconsin, and also winning formerly pro-Trump Arizona, Biden reached 264 electoral votes against 214 so far for Trump.
To reach 270 he was hoping next to add the six electoral votes from Nevada, where he had a small and shrinking lead, or, even better, the larger prizes of hard-fought Georgia or Pennsylvania.
In stark contrast to Trump's unprecedented rhetoric about being cheated, Biden sought to project calm, reaching out to a nation torn by four years of polarizing leadership and traumatized by the Covid-19 pandemic, with new daily infections Wednesday close to hitting 100,000 for the first time.
"We have to stop treating our opponents as enemies," Biden, 77, said. "What brings us together as Americans is so much stronger than anything that can tear us apart."
- Trump claims being cheated -
However, Trump, 74, claimed victory unilaterally and made clear he would not accept the reported results, issuing unprecedented complaints -- unsupported by any evidence -- of fraud.
"The damage has already been done to the integrity of our system, and to the Presidential Election itself," he tweeted, alleging without proof or explanation that "secretly dumped ballots" had been added in Michigan.
Trump's campaign announced lawsuits in Michigan, Pennsylvania and Georgia and demanded a recount in Wisconsin.
In Michigan, the campaign filed a suit to halt vote tabulation, saying its "observers" were not allowed to watch at close distances.
Tension also shifted to the streets, even if so far there has not been the kind of unrest that some feared just ahead of the election, prompting businesses in several major city centers to board up windows.
In Detroit, a Democratic stronghold that is majority Black, a crowd of mostly-white Trump supporters chanted "Stop the count!" and tried to barge into an election office before being blocked by security.
US news networks showed an aggressive pro-Trump crowd also gathering outside a vote counting office in the important Arizona county of Maricopa, which includes Phoenix.
Burly law enforcement officers formed a protective line at the facility's doors. Some of the protesters openly carried firearms, which is legal in the state, while people chanted "Count the votes!"
Just before midnight local time, Maricopa authorities posted new vote totals, with Trump slashing Biden's Arizona vote lead from 79,000 to under 69,000, a gap of 2.4 percent with 86 percent of precincts reporting.
Georgia's largest county of Fulton, which includes parts of Atlanta, was processing ballots through the night. Over a 90-minute period Biden narrowed Trump's lead there from 29,000 votes to 23,000, with 95 percent of precincts reporting.
The tight nature of Georgia's race -- Biden trails Trump by half a percent -- raises the prospect of a recount.
- Be 'patient' -
The US election -- usually touted as an example to newer democracies around the world -- brought statements of international concern, with German Defense Minister Annegret Kramp-Karrenbauer warning of a "very explosive situation."
An observer mission from the Organization for Security and Co-operation in Europe, which monitors votes around the West and former Soviet Union, found no evidence of election fraud and said Trump's "baseless allegations" eroded trust in democracy.
Unless Biden racks up a winning score earlier, the whole contest could eventually wind up being decided by the winner of Pennsylvania, where Trump's initially big lead dwindled rapidly.
The state is a major target for Trump campaign lawyers, who have already challenged its rule on allowing mailed-in ballots received after Election Day to be counted in the US Supreme Court.
Tom Wolf, the state's Democratic governor, insisted on everyone being "patient" and promised all votes would be "counted fully."
The tight White House race and recriminations evoked memories of the 2000 election between Republican George W Bush and Democrat Al Gore.
That race, which hinged on a handful of votes in Florida, eventually ended up in the Supreme Court, which halted a recount while Bush was ahead.
The US Elections Project estimated total 2020 turnout at a record 160 million including more than 101.1 million early voters.