CLEVELAND (AP) — Marked by angry interruptions and bitter accusations, the first debate between President Donald Trump and Democratic challenger Joe Biden erupted in contentious exchanges Tuesday night over the coronavirus pandemic, job losses and how the Supreme Court will shape the future of the nation’s health care.

Fitting for an ugly campaign, the two men frequently talked over each other with Trump interrupting, nearly shouting, so often that Biden eventually snapped at him, “Will you shut up, man?”

“The fact is that everything he’s said so far is simply a lie,” Biden said. “I’m not here to call out his lies. Everybody knows he’s a liar.”

Trump and Biden arrived in Cleveland hoping the debate would energise their bases of support, even as they competed for the slim slice of undecided voters who could decide the election. It has been generations since two men asked to lead a nation facing such tumult, with Americans both fearful and impatient about the coronavirus pandemic that has killed more than 200,000 of their fellow citizens and cost millions of jobs.

The vitriol exploded into the open when Biden attacked Trump’s handling of the pandemic, saying that the president “waited and waited” to act when the virus reached America’s shores and “still doesn’t have a plan”. Biden told Trump to “get out of your bunker and get out of the sand trap” and go in his golf cart to the Oval Office to come up with a bipartisan plan to save people.

Trump snarled a response, declaring that “I’ll tell you Joe, you could never have done the job that we did. You don’t have it in your blood”.

“I know how to do the job,” was the solemn response from Biden, who served eight years as Barack Obama’s vice president.

The pandemic’s effects were in plain sight, with the candidates’ lecterns spaced far apart, all of the guests in the small crowd tested and the traditional opening handshake scrapped. The men did not shake hands and, while neither candidate wore a mask to take the stage, their families did sport face coverings.

Trump struggled to define his ideas for replacing the Affordable Care Act on health care in the debate’s early moments and defended his nomination of Amy Coney Barrett, declaring that “I was not elected for three years, I’m elected for four years.”

“We won the election. Elections have consequences. We have the Senate. We have the White House and we have a phenomenal nominee, respected by all.”

Trump criticised Biden over the former vice president’s refusal to comment on whether he would try to expand the Supreme Court in retaliation if Barrett is confirmed to replace the late Justice Ruth Bader Ginsburg.

With just 35 days until the election, and early voting already underway in some states, Biden stepped onto the stage holding leads in the polls — significant in national surveys, close in some battleground states — and looking to expand his support among suburban voters, women and seniors. Surveys show the president has lost significant ground among those groups since 2016, but Biden faces his own questions encouraged by Trump’s withering attacks.

Trump had arguably his best chance to try to reframe the campaign as a choice between candidates and not a referendum over his handling of the virus that has killed more people in America than any other nation. Americans, according to polling, have soured on his leadership in the crisis, and the president has struggled to land consistent attacks on Biden.

In the hours before the debate, Biden released his 2019 tax returns just days after the blockbuster revelations about Trump’s long-hidden tax history, including that he paid only US$750 a year in federal income taxes in 2016 and 2017 and nothing in many other years. The Bidens paid nearly US$300,000 in taxes in 2019.

Trump, in the debate, insisted that he paid millions in taxes — but refused to say how much he paid in federal income taxes — and insisted that he had taken advantage of legal tax incentives, another angry exchange that led to Biden declaring that Trump was the “worst president” the nation has ever had.

Biden’s performances during the primary debates were uneven, and some Democrats have been nervous as to how he would fare in an unscripted setting. But his team also viewed the night as a chance to illuminate Trump’s failings with the pandemic and economy, with the former vice president acting as a “fact checker on the floor” while bracing himself for the onslaught that was coming.

The tumult of 2020 was difficult to overstate: COVID-19 has rewritten the rules of everyday life; racial justice protests have swept into cities after several highly publicized killings of Black people by police, and the death of Supreme Court Justice Ruth Bader Ginsburg allowed Trump to nominate a conservative jurist to replace a liberal voice and perhaps reshape the high court for generations.