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After a scrappy exchange on the Supreme Court, Chris Wallace introduces the next topic, Covid-19. The moderator manages to calm the cross-talk a little and ask his question. He says it's an awfully serious subject, adding: "let's try to be serious about it".

With more than seven million US cases and some 200,000 deaths, Wallace asks: "Based on what you have said and done and so far what you have said you would do starting in 2021, why should the American people trust you more than your opponent to deal with this public health crisis?"

"The president has no plan," Biden begins by saying.

One of the first shows of irritability from Joe Biden after Trump repeatedly asks him to say whether or not he would expand the Supreme Court if he wins, to eliminate the coming conservative tilt.

"Will you shut up man?" replies Biden, adding: 'Keep yapping, man.'

Trump shoots back: "The people understand, Joe - 47 years [in Washington] you've done nothing."

Anthony Zurcher
BBC North America reporter

The opening topic for tonight’s debate was the Supreme Court, but Joe Biden quickly tried to turn the discussion to the Affordable Care Act (aka Obamacare) – which is at risk because of a pending case before the court.

Trump accused Biden of supporting socialised medicine and pushing to do away with private insurance, prompting the Democrat to reply that wasn’t in his plan – and if Democrats wanted something different, they would have nominated one of his primary opponents.

"I am the Democratic Party right now,” Biden said. “The platform of the Democratic Party is what I approved.”

One of Trump’s goals during this debate – and throughout the whole campaign – is to paint Biden as beholden to the left wing of his party. Biden, in his very first exchange with the president, outlined his rebuttal.

OK, there's a lot of talk about healthcare already tonight. Here's what you need to know.

The candidates are debating Obama's signature health law, the Affordable Care Act, a public health insurance scheme that brought health coverage to millions of uninsured Americans.

Congressional Republicans last year finally succeeded in repealing the Obamacare requirement that people buy health insurance or pay a tax penalty - Trump has been touting this during the debate as one of his key accomplishments.

Read more about the law and how Trump has worked to dismantle it here.

"As the moderator, we are gonna talk about Covid in the next segment," jumps in Wallace after Trump makes a claim that Biden would not have handled the pandemic well.

After Wallace tells Trump that he has not yet come out with a comprehensive health plan to replace Obamacare, Trump argues that Wallace is wrong.

"Yes I have. Course I have," insists Trump.

"I am the moderator of this debate and I would like you to answer my question," says Wallace, adding that the executive order Trump signed earlier this month was "largely symbolic".

"I guess I'm debating you, not him [Biden], but that's ok," responds Trump.

Image source, Reuters

Trump claims that the coronavirus death toll - over 200,000 Americans - would have been much higher if Biden had been in charge when the pandemic hit.

"It would be 200 million people because you would have been late on the draw," says Trump.

"You would have been much later," to ban travelers from China, continues Trump. The president has claimed that placing travel restrictions on visitors from the country helped prevent infections.

Biden says that the American people get a chance to weigh in on Supreme Court decisions in elections - which we're in the middle of now.

"That's the only way the American people get to express their view - by who they elect as president and who they elect as vice-president," Biden says.

Biden goes straight into what another Trump justice pick might mean for healthcare (and Obamacare) - a key part of the Democratic platform and one that won them votes during the 2018 midterm elections.

Image source, Getty Images

Taking the first question, Trump is calm, defending his new Supreme Court nominee Amy Coney Barrett who opponents say will push the top US judicial body further to the Right.

She's "good in every way", Trump says. "I think she will be outstanding."

And Trump defends the timing of the nomination as well. If the Democrats had the chance, they would put forward a nominee and try to get them confirmed too, Trump says.

"As far as the say is concerned, the people already had their say," Trump adds, regarding his role in picking the Supreme Court justice.

"I’m not elected for three years I’m elected for four years," he says.

Host Chris Wallace begins by asking why Trump should be able to nominate the next Supreme Court justice, when Biden argues that the next justice should be chosen after the election.

To each candidate, he asks "why are you right?"

"We won the election. Elections have consequences," says Trump.

"We won the election and therefore we have the right to choose her."

Image source, Reuters

And we're off - the first presidential debate of the 2020 election has just begun.

On stage, we've got President Trump, challenger Joe Biden and their moderator, veteran TV journalist Chris Wallace of Fox News. He'll pose six questions in six segments, with 15 minutes for answers.

The audience has promised to be silent except for a round of applause now, as the two settle in at their podiums.

First Lady Melania Trump and Jill Biden are also present, watching from socially distanced seats.

There were no handshakes this time, however, one of several Covid-19 measures in place.This is the first of three times the two candidates will battle out the issues on TV before voters cast their ballots on 3 November.

Just minutes before he takes the stage, Trump's wife, daughters and sons have taken their seats in the audience.

Minutes later, Ivanka Trump posted a photo featuring some of her most famous family members - step-mother Melania Trump, half-sister Tiffany Trump and sister-in-law Lara Trump.

...Until we get to witness this first televised presidential debate between Donald Trump and Joe Biden.

If you're still wavering on who to vote for - or can't vote but take the issues as seriously as the pantomime - here's a timely reminder of where the pair stand on some key voter priorities:

What Joe Biden wants to achieve - and Donald Trump's main policies.

You can watch the event via the play button at the top of this page.

Image source, bbc

Imagine you're in the moderator's seat: what would you ask the President of the United States and his challenger? We've been reading your responses, and here are a few from folks around the world.

• What role do you think America should play on the world stage? - Daniel, 31, Salzburg, Austria
• Why are you the person in the best position to inspire the next generation about the potential of politics and public service? - Tom, 20, Sheffield, UK
• What can we expect for the marijuana industry in the next four years - are states with legal marijuana going to be cracked down upon by the federal government? - Andrew, 20, Gulfport, Mississippi
• How will each of you deal with unemployment due to businesses closing during Covid-19? - Melanie, 78, Columbus, Ohio
• What are the strong or positive aspects of your opponent? - Mats, 64, Sweden

We'll share more from our readers throughout the night. You can submit your own questions here.

Image source, Reuters

As the stage awaits the players in Ohio, Trump's pick for the Supreme Court, Judge Amy Coney Barrett, is in Washington and has just left Capitol Hill after meeting with Republican lawmakers for nine hours.

Republicans are trying to confirm her nomination quickly, but Democrats argue that it should be the winner in November who chooses the high court's ninth seat.

Recent national polls, external show that a slim majority of Americans agree.

But Democrats have few options to block her nomination before November. If Democrats win the White House and Congress, there is talk of expanding how many judges sit on the court as a way to prevent the coming conservative tilt.

Read more:

Amy Coney Barrett: Who is Trump's Supreme Court pick?

Image source, Getty Images

The host of tonight's debate is Chris Wallace, and the 72-year-old is not just any Fox News anchor. He's made a name for himself for being precisely not the Trump-cheerleader that some of his other high-profile colleagues are often accused of being.

Instead, he's seen as a serious, interrogative and even-handed journalist, with a measured delivery that at times seems to hark back to the TV news anchors of the 1960s and 1970s.

And this won't be his first debate rodeo. Wallace, who had a long career at other broadcasters before joining Fox, burnished his long-standing reputation for fair treatment of both sides of the US political aisle in 2016, when he became the first Fox News anchor to host a presidential debate.

You may remember him more recently from his one-on-one interview with Trump earlier this year, when the veteran journalist told the president that he, too, took the cognitive test Trump had boasted about "acing".

Read more about Chris Wallace here.

Ok, it's time to grab the popcorn: just 30 minutes till the debate fireworks start. Stick with us for live reporting and real-time analysis.

We'll have all the best lines, fact-checking, and context - plus a live video feed of the event at the top of this page - and clips of all the key moments.

Image source, The Washington Post via Getty Images

Some interesting insight into what Americans have been searching for around the debate today from Google Trends.

We've been doing our best to help you out, though if you're here we're assuming you know that kick off is in a little over half an hour. Still time for you to read our excellent primer on the night's events - including what to watch for and why it all matters.

Barbara Plett Usher
BBC News, Washington

Image source, Getty Images

Under a Joe Biden presidency the US would re-enter the Paris Climate Agreement, rejoin the World Health Organization and seek to lead a global coronavirus response.

The Biden campaign describes this as a plan to restore American leadership and a promise to reverse the disruptive, unilateralist instincts of President Donald Trump. This would be more style than substance, counter some Republican analysts, who argue that the Trump administration has engaged the world, just with sharp elbows.

Biden takes seriously the bruises inflicted on allies. Repairing the damage done would be at the top of his priority list - even if some core policy demands, such as pressure for Nato members to spend two percent of GDP on defence, stayed the same. But there would also be sharp policy turns: an aggressive focus on climate change, and an increase in refugee admissions.

Expect change in the Middle East too: not in fulsome support for Israel -although the left wing of the Democratic party has pushed for a greater emphasis on Palestinian rights- but on Iran and Saudi Arabia. Biden would re-enter the Iran nuclear agreement if Tehran resumed its commitments. And he’s said he'd end US support for the Saudi-led war in Yemen.

Donald Trump is already sure the debate will go down in history - or at least that's what he's telling supporters.

Before he even takes the stage, Trump's campaign has pitched for fundraising dollars off of tonight's event, boasting that the candidate showed the American people he "will ALWAYS fight to put America first".

And he's not the only one hoping for a post-debate fundraising boost. Earlier today, Biden supporters received an email from former President Barack Obama, asking them to "show Biden we have his back" ahead of his performance.

Image source, Getty Images

We're counting down until Biden and Trump take the stage - and those in Cleveland are geared up for the presidential face-off.

Masked security are keeping an eye on anti-Trump demonstrators outside the venue - some with signs featuring the late Supreme Court Justice Ruth Bader Ginsburg, and several with inflatable balloons depicting the president as a baby.

Meanwhile, Joe Biden made friends with his temporary neighbours a couple of hours ago and Ivanka Trump flew in to support her father in person.

Image source, EPA

Image source, Reuters

Image source, Reuters

Image source, Getty Images

Image source, Getty Images