America was wracked with nervous energy as Election Day dawned.

Katie Whelan, a high school history teacher from New Jersey, recounted that she crossed the Pennsylvania border to knock on doors over the weekend for Joe Biden in the key battleground.

The previous night, Whelan said, she had awakened from a panic dream involving Hillary Clinton and the dread of falling just short at the ballot box. “She was like, ‘Honey, I’ve been there’,” Whelan recalled Clinton telling her in the dream.

Adding to her anxiety, Whelan could not tell if the nightmare was set in 2016 or 2020. “I stood over the sink and drank three pints of water,” Whelan said. “And I said to myself, ‘I better get canvassing’.”

Much of the US is on edge, as if the often-predicted “most important election of a lifetime” had finally arrived.

Undeterred by the pandemic, Americans have already displayed an uncommon determination to have their voices and votes heard this year. Nearly 100 million cast their ballots ahead of Election Day, shattering records as they sent in their votes by mail.

Wearing face masks and standing spaced apart, voters waited at polling stations early on Tuesday to choose a President on an Election Day marked so far by orderliness and short lines, even as major cities braced for potential unrest.

The masks and boarded-up stores in many city centres were reminders of two of the issues shaping 2020’s polarising elections, with Covid still ravaging parts of the country after a summer of sometimes violence-marred protests against police brutality and racism.

The Federal Bureau of Investigation is looking into a spate of mysterious robocalls urging people to stay home on Election Day, a Department of Homeland Security official said. The Washington Post reported that an unidentified robocaller placed an estimated 10 million calls in recent weeks warning people to “stay safe and stay home”.

Poll workers guessed the short lines in many places were because of the unprecedented wave of advance voting. The most closely watched results are expected to trickle in on Wednesday morning in India.

In Atlanta, Georgia, about a dozen voters were lined up before sunrise at the Piedmont Park Conservancy. First in line was Ginnie House, shivering in the cold, waiting to cast a vote for Democratic candidate Biden, a former Vice-President seeking to replace President Donald Trump, a Republican, in the White House.

“I lost my absentee ballot and I’m not going to miss this vote,” said House, a 22-year-old actor and creative writing student, who had flown back to Atlanta from New York just for this purpose.

In Hialeah, a predominantly Cuban-American suburb of Miami, Marcos Antonio Valero, 62, was voting for Trump, as he had done in 2016. He said he took the day off from his job as a construction worker to cast his ballot in person because he did not trust voting by mail.

He made no prediction. “It’s a secret, a mystery,” he said. “No one knows how it’s going to end until we all know.”

At a polling station in Houston, Texas, Andy Valadez was blowing a shofar wrapped in a US flag. A shofar is a trumpet used in Jewish and some Christian ceremonies and, in this instance, as a way to pray for a Trump victory, according to Valadez.

“We want to pray for a fair election,” the 55-year-old marketing executive said.

“We believe in America and want everyone to have a safe voting experience.”

President Trump said on Tuesday morning in an interview on Fox & Friends: “I think we will have victory. But only when there is victory. You know, there is no reason to play games.”

Biden returned to his Pennsylvania birthplace, Scranton. As he chatted with supporters, Biden used track and field analogy about finishing the race: “You got to run through the tape, man. You got to go all the way through the tape.”