Donald Trump has refused to denounce the QAnon conspiracy theory, which falsely claims the US government is controlled by a "deep state" cabal of anti-Trump Satanist paedophiles.
In a combative televised town hall the US president repeatedly disavowed white supremacy. But when asked to do the same with QAnon, he said: "So, I know nothing about QAnon. I know very little. What I do hear about it, they are very strongly against paedophilia. I do agree with that."
He added: "I know nothing about it. I do know they are very much against paedophilia, they fight it very hard, but I know nothing about it."
The president was subsequently questioned over his decision to retweet a false conspiracy theory, from a QAnon-linked Twitter account, suggesting that Navy Seals killed a body double of Osama bin Laden, and that the Obama administration covered it up.
Mr Trump said he was just "putting it out there" and "people can decide for themselves".
Savannah Guthrie, the host of the town hall, responded: "I don’t get that. You’re the president, not someone’s crazy uncle."
Defending his handling of the pandemic, Mr Trump cited statistics saying coronavirus was up 2,500 per cent in the United Kingdom.
The president said: "Look at what's going on in Europe. Massive spikes. They've done a very good job, but now you take a look today at the UK, and Spain, and France, and Italy, there's tremendous spikes."
Ms Guthrie suggested the US death rate was higher. But, producing a piece of paper with figures on it, Mr Trump said: "I have things right here that will tell you exactly the opposite.
"So, the UK is up 2,500 per cent. The European Union is up 722 per cent, and the United States is down 21 per cent."
Mr Trump's town hall took place in Miami and was broadcast by NBC. Joe Biden held a simultaneous televised town hall in Philadelphia on ABC.
I will be doing a major Fake @NBCNews Town Hall Forum, live tonight from Miami, at 8:00 P.M. They asked me to do it in place of the Rigged Steve Scully (he is now suspended from @cspan for lying) Debate. I wonder if they’ll treat me as well as Sleepy Joe? They should!
— Donald J. Trump (@realDonaldTrump) October 15, 2020
In Miami, Mr Trump disclosed that doctors had determined his lungs were "a little bit infected" when he was hospitalised with the virus.
He declined to say whether he took a coronavirus test on the day of the first presidential debate, saying he did not remember. He tested positive two days after the debate.
The president went on to say that "people with masks are catching it all the time" and repeated a claim that "85 per cent of people wearing the mask catch" the virus. The US Centers for Disease Control and Protection has rejected that figure.
— Mikey Smith (@mikeysmith) October 16, 2020
Challenged on his tax returns Mr Trump admitted he did owe money but said "$400 million is a peanut" and he was "extremely underleveraged".
Asked if he would commit to a peaceful transfer of power, Mr Trump said "the answer is yes" but he wanted an "honest" election.
When Ms Guthrie said his FBI director had said there was no evidence of widespread ballot fraud, the president responded: "Well, then, he's not doing a very good job."
Mr Trump also denied that he was told in the Oval Office, by his national security adviser in January, that the coronavirus would be the biggest national security threat of his presidency.
In Philadelphia, Mr Biden said: "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."
Mr Biden put on his mask when leaving the stage to be closer to questioners.
The Democratic indicated he would announce a definitive stance before the election on the controversial idea of adding more seats to the nine-member US Supreme Court. The court currently has a conservative majority.
Over 215,000 Americans have died from COVID-19, and what is President Trump doing?
— Joe Biden (@JoeBiden) October 16, 2020
Mr Biden said he would take a virus vaccine if it emerged while Mr Trump was still in office. He said: "If the body of scientists say it’s been tested, they’ve gone through the three phases, yes, I would take it, and I’d encourage people to take it."
Mr Biden went on to suggest that, if a vaccine met that criteria, he would like to make it mandatory if elected, just as he would like to make masks mandatory.
He conceded that, as president, he would not have the power to make vaccines mandatory, but said he would call upon state governors, local mayors and other city officials to encourage the public to take it.
Asked what he would do if he lost the election, Mr Biden said he would return to teaching at the University of Pennsylvania and work to end racial injustice.