President Donald Trump gave a combative, at times agitated defense of his Covid-19 response Thursday while his election challenger Joe Biden -- offering a glaring contrast in style in a rival televised town hall -- -- accused him of doing "nothing" to end the pandemic.

The dueling appearances, scheduled at the same time on rival networks, showed Biden giving unflashy, often in-depth answers to voters in the audience, while Trump delivered a fiery defense of his presidency.

Trump, who is well behind in the polls ahead of the November 3 election, was especially under pressure when it came to the coronavirus that has killed 217,000 Americans and inflicted deep economic damage.

Joe Biden and Donald Trump
Their second head-to-head debate was cancelled, but Joe Biden and Donald Trump will hold separate town hall events at the same time instead Photo: AFP / JIM WATSON

"We're rounding the corner," Trump insisted with his usual optimism, even as swaths of the United States see sharply rising caseloads.

But pressed by the host of the NBC town hall in Miami, he became quickly frustrated, especially when he was asked about his previous lukewarm denunciations of extremist right wing groups in the United States.

He notably refused to denounce QAnon, a bizarre conspiracy theory movement that believes Trump is fighting a "deep state" linked to a mysterious global elite running the world's governments, while also trafficking in child sex.

US Presidential debate
The first of three scheduled presidential debates was widely criticized for descending into an angry shouting match as Donald Trump attempted to inflict a late wound to Joe Biden's campaign Photo: POOL / Olivier Douliery

Trump said "I know nothing about QAnon," and then continued to say that he liked the shadowy group's position being "very much against pedophilia."

The president entered calmer waters when fielding a series of more comfortable questions from members of the audience, one of whom sparked applause with her statement: "You have a great smile."

"You're so handsome when you smile," she said.

Donald Trump
Trump says he 'felt like Superman' after his experimental COVID-19 treatment Photo: DC POOL

By contrast, Biden's appearance on the rival ABC news network mirrored his generally low key campaign, with promises of bipartisan healing in divided Washington and aiming steady fire on Trump's coronavirus record.

Joe Biden and Donald Trump
Opinion poll averages for Donald Trump and Joe Biden in battleground state Arizona just weeks before the US presidential election on November 3, 2020 Photo: AFP / Gillian HANDYSIDE

"We're in a situation where we have 210,000 plus people dead and what's he doing? Nothing. He's still not wearing masks," Biden said of Trump at the event in Philadelphia.

His standout comments at a time of profound political conflict in the country were when he vowed to change the atmosphere, saying "grudges don't work."

"We've got to change the nature of the way we deal with one another," Biden said.

President Donald Trump campaign
President Donald Trump has hit the ground again with back-to-back campaign rallies Photo: AFP / SAUL LOEB

"What I will be doing if I'm elected president, the first thing -- and not a joke... I'm going to pick up the phone and call them and say, 'Let's get together.'"

Donald Trump
US President Donald Trump's son Barron caught coronavirus, his mother, First Lady Melania Trump, revealed Photo: AFP / Alex Edelman

Originally, both candidates had been meant to meet Thursday for what would have been their second of three presidential debates.

The first debate, which took place in Philadelphia, was a brutal affair in which Trump repeatedly talked over the top of Biden and the Democrat told him to "shut up." The follow-up, however, was scrapped after organizers switched to a virtual format, citing Trump's coronavirus infection, and the president refused to accept the arrangement.

Trump, who says he is clear of Covid-19 and got back on the campaign trail Monday, has rallies booked around the country for every night this week.

He predicted to supporters at a rally in North Carolina earlier Thursday that Biden would be given an easier time over on ABC. "I'm being set up tonight," he said.

The decision by NBC to accept a Trump appearance at the same time as Biden's town hall likely meant that few Americans would get to see and contrast the two men.

With only 19 days until the election, Trump is now running out of time to overtake Biden.

Even a close US Senate ally to Trump, Lindsey Graham, said Thursday Biden may be on his way to victory.

"You all have a good chance of winning the White House," he told Democratic colleagues at a hearing on Trump's conservative Supreme Court nominee Amy Coney Barrett.

And despite Trump's insistence that the coronavirus pandemic is in the rear view mirror, it continues to disrupt the tense presidential election.

Following Trump's temporary time out from the campaign while he recovered last week, Biden's vice presidential running mate Kamala Harris has now put her own travel on hold after her communications director tested positive.

Harris staffer Liz Allen and a flight crew member were diagnosed late Wednesday.

Harris did not need to quarantine, the Biden campaign said, but "out of an abundance of caution" would cancel travel and campaign virtually until October 19.

Biden has reported multiple negative coronavirus tests since Trump's Covid-19 diagnosis on October 1, the latest dating from Thursday.

The campaign said that yet another person who tested positive had traveled on Biden's plane this week but had been so far away that the candidate was in no danger and doctors said "there is no need" for him to quarantine.

While Trump boasts of being "immune" to the coronavirus after recovering, he continues to be dogged by the pandemic's fallout.

On Wednesday, his wife, First Lady Melania Trump, revealed that their son Barron, 14, had contracted the virus, but was now negative.

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