President Donald Trump and Democratic challenger Joe Biden went head-to-head in their final debate of the election campaign at Belmont University in Nashville, Tennessee.
Special measures were in place because of the Covid-19 pandemic, including plexiglass barriers that were put between the two candidates' podiums.
They were removed before the debate following negative tests for Trump - who spent three days in hospital after testing positive earlier this month - and Biden.
Dr Anthony Fauci, the top US expert in infectious diseases, was consulted and both campaigns agreed for the plexiglass to be removed.
President Trump's daughters Ivanka and Tiffany arrived wearing masks.
At the last presidential debate, First Lady Melania, Ivanka, Donald Trump Jr, Eric Trump and several guests entered the hall with masks on but took them off once seated, in violation of the debate rules.
The first lady - who had also contracted coronavirus - walked into the debate hall also wearing a mask.
Critics of the last debate claimed that it became an unintelligible squabble, so this time organisers introduced mute buttons on their microphones, so Biden and Trump could deliver statements without interruption from the other.
The debate moderator was Kristen Welker, an NBC News anchor and White House reporter.
The debate was divided into six segment topics: Fighting Covid-19, American Families, Race in America, Climate Change, National Security, and Leadership.
The US has the highest total number of cases of coronavirus, with more than 8.3 million infections, and the highest death toll in the world, of more than 220,000.
Since the last debate earlier this month, 16,000 Americans have died from Covid, Welker says. How would Trump lead in the next stage of the crisis?
He says spikes across the nation are "now gone", and "spikes and surges in other places they will soon be gone".
"I can tell you from personal experience... I had it, I got better."
Biden gives his response: "If we just wore these masks," he says, holding up his own, "we could save 100,000 lives."
He says there is an expectation that the US will see another 200,000 deaths by the end of the year.
The Biden plan then is making sure everyone is encouraged to wear masks, make sure there is rapid testing, and set up national strategies to open up schools and businesses.
"We're learning to live with [the virus]," Trump says.
Biden hits back: "People are learning to die with it."
The next topic is US national security.
Russia and Iran are both working to influence the election, moderator Kirsten Welker says, asking what Biden and Trump plan to do about the claim from US intelligence officials.
"Any country that interferes in American elections will pay a price," begins Biden, saying it has been his clear position throughout his political career.
The debate about national security turns into a discussion about foreign political influence, with both men flinging accusations at each other.
"I never got any money from Russia. I don't get any money from Russia," Trump says, claiming that Biden's family has been enriched by Russian oligarchs, without providing evidence.
Biden responds: "I have never taken a single penny from any country whatsoever." He says Trump has been enriched by foreigners, including the Chinese.
A report by the New York Times this week indicates that Trump has a Chinese bank account and may have paid more taxes to China than the US in recent years.
The debate turns to American families, focusing on access to health care.
Trump argues that his "law and order" message saved cities from urban poverty and criminal migrants.
Speaking of Obamacare, Biden says he has a plan to expand coverage, aptly named "Bidencare".
"What I'm going to do is have Obamacare with a public option," he says.
On the next topic of Race, Biden says: "There is institutional racism in America."
Trump repeats his claim of being the best president for black Americans - with the possible exception of Abraham Lincoln, who ended slavery.
On the topic of climate change, Biden says he would undo Trump's decision to withdraw from the Paris Climate agreement.
Trump says he loves the environment and wants the cleanest water and air. "We have the best, lowest number of carbon emissions," he says.
By contrast, he accuses China and Russia of being "filthy".
The final topic of the night is Leadership.
Welker asks the candidates what they would say in their inauguration speech to the voters who did not want them to win.
"Success is going to bring us together. We are on the road to success," Trump says.
"I'm gonna give you hope," Biden says when asked the same question. "We're going to choose science over fiction. We're going to choose hope over fear."
At the end of the debate, First Lady Melania and by Dr Jill Biden join their husbands on stage.
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