The debate opens with the defining issue of the US election - and 2020 itself: the coronavirus pandemic. It's driven a record volume of early voting and it's an uncomfortable issue for Trump.

He beat his own encounter with the virus - aided by the best medical care in the country - but the last time a majority of Americans approved of his administration’s handling of the pandemic was back in April, research suggests.

On the stump, Trump has recently been claiming that the US is “rounding the turn” on the pandemic, despite the weekly case average rising in 48 of the country’s 50 states.

Biden says the situation is deteriorating. “As my grandfather would say, this guy’s gone around the bend if he thinks we’ve turned the corner. Turning the corner? Things are getting worse,” he told a rally at the weekend.

First Lady Melania Trump, who has had coronavirus in the three weeks since the last presidential debate, walked into the debate hall wearing a mask.

The Commission on Presidential Debates has made it clear that masks must be worn by everyone present in the hall tonight.

Last time around, Melania Trump, Ivanka Trump, 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.

Image source, Getty Images

The final presidential debate before Election Day has just kicked off.

On stage - without plexiglass barriers, but 12ft apart - Donald Trump, Joe Biden and their moderator for the night, Kristen Welker.

We saw the families and guests take their seats - Jill Biden and Melania Trump are in attendance - the latter out for the first time since her Covid diagnosis. Both were wearing masks.

Remember: there will be mic muting tonight, but only during each candidate's two-minute initial response to the questions. It's open season during the discussion segments.

What sort of night are we in for. The easy listening channel, or heavy metal? We're about to find out.

The Biden camp is out with a new statement, denouncing Trump's decision to invite a surprise guest, Tony Bobulinski, who claims to be able to corroborate disputed reporting about Hunter Biden's business dealings.

"Vice-President Biden has actually released his tax returns - unlike President Trump - and there is no indication he ever got any money from anybody in these business deals," said spokesman Andrew Bates.

"Joe Biden has never even considered being involved in business with his family, nor in any overseas business whatsoever."

"This is a desperate, pathetic farce executed by a flailing campaign with no rationale for putting our country through another four years of hell," he added.

Trump broke decades of political tradition by refusing to release his tax returns while running for office. The New York Times claims to have seen Trump's books and says he may owe millions of dollars to foreign entities and has paid more taxes to China than the US in the past 20 years.

Read more about the claims about Biden's son Hunter:

Hunter Biden: What was he doing in Ukraine and China?

He's almost certainly not sending his own tweets at this point in time, but Joe Biden wants the world to know he's...

We're watching tonight's debate with voters from battleground states - the places that will ultimately decide the election.

Next up, Eliana. After becoming disillusioned with the left, she now supports the policies of the Republican Party and backs the re-election of Donald Trump. She is the president of her local young Republicans group and a former professional dancer. She won the national television competition 'So You Think You Can Dance' in 2012.

What are you looking for in the final presidential debate?

I’m interested in seeing Trump speak more directly about his mass accomplishments the way Pence shared the information in the vice-presidential debate. Biden will speak himself in circles with flip-flopping opinions of policies, proven corruption denials, and tacky name calling like “clown”.

Why do you support your candidate?

Trump is the only politician who has made promises and kept them. History breaking economic expansion, moving the US embassy to Israel, being an anti-war advocate, functional peace in the Middle East, lowering cost of medicine for all, prison reform, pro-freedom of speech and anti-censorship, shall I go on? This election will show that the big tech media complex can’t control an election. The American people see what’s the truth regardless of blatantly false journalistic propaganda.

Eliana is a member of our US election voter panel. We want to hear from you - what questions do you have for our focus group tonight?

Barbara Plett Usher
BBC News, Washington

Image source, Getty Images

Like Donald Trump, Joe Biden wants to end the "forever wars" in Afghanistan and Iraq, but he would keep a small troop presence in both to help battle terrorism.

On Russia, the relationship at the top would certainly look different - likely little else.

Trump often seemed ready to personally forgive Vladimir Putin for violating international norms. But his administration punished Russia with sanctions, and that would probably continue under a Biden presidency.

On China there is rare bipartisan agreement to get tough with Beijing over trade and other issues; the question is one of tactics. Biden would continue Trump’s policy of countering China's "abusive economic practices", but jointly with allies, instead of Trump's preference for unilateral trade deals.

The Trump administration's sharp elbows have been successful in winning global support for a boycott of Chinese communications technology. That's part of a serious escalation in US efforts to push back against Beijing, anchored in accusations that it mishandled the coronavirus.

This campaign is led by Trump's China hawks. Biden would more actively seek areas of cooperation with a rising China.

We're watching tonight's debate with voters from battleground states - the places that will ultimately decide the election.

Andrew is an undecided voter leaning toward Joe Biden, but wishes he had better options to choose from.

What are you looking for in the final presidential debate?

An actual look into what the next four years will be like under the future president. We are at a crucial point in history where our environment is in peril, our economy is in peril, and the health of so many Americans is in peril. We need to address all these issues, not just pick and choose.

Why are you undecided?

Both sides are making it hard to vote with heart and mind. I have seen crazy things said by both sides that make me uncomfortable. I want a sign of real leadership with logic, compassion, and clear vision. As a father of two young children and a hospitality industry employee, I am concerned about how restaurants and small businesses will make it out of this pandemic.

Andrew is a member of our US election voter panel. We want to hear from you - what questions do you have for our focus group tonight?

Image source, Reuters

To coincide with the final debate tonight, UK comedian Sacha Baron Cohen is hosting a global viewing party of his upcoming film.

You may have heard Cohen - known for his character Borat - in the news recently because his latest flick reportedly has some "compromising" scenes featuring Trump lawyer Rudy Giuliani. (More on that here.)

Presidential debates have sometimes had to compete for viewership with big sporting events - but being up against a film premiere about a fictional Kazakh trying to score a deal with one of the candidates is a first.

Jon Sopel
BBC North America Editor, Nashville

This is the last major set piece of this protracted presidential election campaign. It will be carried on the all the major TV networks, the audience will be huge, the stakes high. In football terms Joe Biden will be happy to play out a nil all draw. Donald Trump, trailing in the polls needs to score a big win.

Just like last time round, he’s likely to go on the attack from the off. And he will try and go after the Democratic candidate’s son business dealings, and in particular emails apparently found on Hunter Biden’s laptop from a period when his father was vice president. Joe Biden has to decide whether he just tries to brush this off, or engages. But the first topic of discussion will be the handling of the coronavirus outbreak, a subject that will see the president on the defensive, with cases surging.

The independent body running the debate has brought in a new innovation: the mute button. During the two minutes when each man will have the chance to set out their case on a given topic, the other person’s microphone will be turned off. The hope is that this will stop the unseemly food fight that unfolded in the first debate.

Another important point – 42 million Americans have already voted, that is nearly a third of the total number of ballots cast in 2016. And that means whatever unfolds this evening will have no impact on these people. But will that mean tonight be less heated? Not a chance

Image source, Getty Images

Shortly before the final presidential debate, the Food and Drug Administration (FDA) issued formal approval for the first treatment against Covid-19 in the US.

Remdesivir, which is delivered intravenously by doctors, was given to Trump when he caught coronavirus and was treated for three days in a military hospital.

The drug is approved for patients that are "12 years of age and older and weighing at least 40kg (88lbs)," the FDA said.

Remdesivir, made by Gilead Sciences Inc, received emergency use approval in May, but today's move formally labels it as safe.

Read more: US gives full approval for antiviral remdesivir drug

Laura Trevelyan
BBC World News America presenter, Nashville, Tennessee

Atmospheric, dramatic lights have just been switched on at the debate hall here at Belmont University. The candidates are due to arrive shortly. The special guest of the Trump campaign Tony Bobulinski is here, claiming to be a business associate of Hunter Biden’s, as the president hopes to repeat his 2016 debate trick when women who said they’d been sexually assaulted by President Clinton showed up to his debate against Hilary Clinton. The Biden campaign says this shows the president has no closing argument for his campaign.

As the candidates head to the debate hall - the trees outside are lit up in the colors of the two political parties. Advisers to Mr Biden say he’ll use tonight to speak directly to the American people. Mr Trump’s strategists say he should allow Joe Biden to speak, and let his rival make mistakes.

Image source, Reuters

The countdown is on.

In just one hour, Joe Biden and Donald Trump will share a stage for the last time before the election.

They'll cover a wide array of topics - from Covid-19, to race, to the American family - and will also surely go off script.

We'll stream the debate right here so stick around for our live coverage.

US astronaut Kate Rubins wasn't going to let not being on Earth get in the way of casting her ballot - so she voted from the International Space Station (ISS) today.

She's currently 253 miles (408km ) above this planet, having started a six-month stint on the orbiting station last week.

If you're wondering how her vote will be counted, Nasa described it as a kind of absentee voting.

A clerk's office in Houston, Texas, emailed a secure electronic ballot to the ISS, and Rubins sent it back.

In fact, it's not her first time voting from space - Rubins also cast her vote from the ISS during the 2016 presidential election.

Tara McKelvey
BBC News, Washington

Long before anyone else had heard of Joe Biden’s son Hunter, people in Kansas and Arkansas were talking about him and his business dealings.

These conservative Midwesterners see Hunter and his father as symbols of corrupt Washington, and they admire the way that Trump has tried to take them on and root out corruption.

True - some of the recent disclosures about Hunter appear to be based on elusive sources. Yet that matters little to these voters. They say they are not entirely sure what he has done, but they know there’s something going on.

During the debate, they will be watching closely to see how Biden reacts when the subject of his son’s business deals comes up. They want Biden and the other politicians in Washington to be held accountable for their actions.

“They have forgotten who their bosses are,” one Arkansan, Joyce Smith, a retired nurse, tells me. “We, the people, are the ones that put them there."

Read more about her and other conservatives here.

Image source, Getty Images

Along with Trump and Biden, NBC's Kristen Welker will also be in the hot seat tonight as she moderates the final debate.

In doing so, she'll become only the second black woman in US history to moderate a presidential debate.

She follows Carole Simpson, who moderated a debate between Bill Clinton, George H W Bush and Ross Perot in 1992.

The veteran journalist Gwen Ifill moderated vice-presidential debates in 2004 and 2008.

Laura Trevelyan
BBC World News America presenter, Nashville, Tennessee

It's been three weeks since the last debate between Donald Trump and Joe Biden, and a lot has changed.

Since then, the president himself has been infected with coronavirus. More than a thousand people in the US died yesterday from Covid-19. There are frantic talks in Washington about a stimulus bill to help the millions of Americans who are struggling financially.

Going into tonight's debate, Trump looks to be trailing in the polls. He's looking tonight for a reset, to make an impact - with just 12 days to go until Americans vote. It's worth noting, though, that more than 40 million have already voted.

The pandemic is undoubtedly going to be a heated discussion point tonight. Cases have been rising across the US, and students on college campuses where there have been spikes are often blamed for contributing to the surges.

There have been at least 178,000 cases and 70 coronavirus-related deaths on US campuses since the beginning of the pandemic, a New York Times survey found. Between early August and September, cases among Americans aged 18-22 more than doubled, according to the US Centers for Disease Control.

We asked college students on our voter panel to weigh in.

"I like the president's message of 'don't be afraid'," a young Republican told us. "His high profile case and recovery should give us confidence that this can be overcome."

One Democrat told us she felt the president's response has been "ignorant and selfish". "He received the best medical care in the world but tries to compare his experience to be the same as everyone else's."

Read the full story here.

Take a break from all the scrolling and let’s chat for a moment!

We know politics can get complicated - that’s why we’re here. If you’ve got questions about the US election, BBC journalists want to answer them.

Submit your questions here.

And you can check out some election questions we've already answered here:

• Your top questions answered
• What is the electoral college?
• How Trump and Biden compare on abortion
• What do young Republicans think of Trump?

The Biden campaign has just released a statement saying the candidate and his wife Jill will be visiting two counties outside Philadelphia, Pennsylvania - Bucks and Luzerne - on Saturday, to speak about "building back the economy better for working families".

The Democratic candidate's schedule has been light this week as he prepared for tonight's debate. Meanwhile, Trump's travel schedule has continued at a breakneck pace.

According to the Bucks County Courier Times, external, local Republican officials say there is a "99 percent" chance that the president will be holding a rally in Bucks County on Monday.

Trump's campaign schedule, which does not yet include Monday, has rallies in North Carolina, Ohio and Wisconsin on Saturday, and New Hampshire on Sunday.

Democrats condemn Trump for holding mass gatherings amid the coronavirus pandemic, and have enacting social distancing measures at their own campaign events. Trump, on the other hand, mocks the Biden events and says they have to be small because no one is interested in turning up.