Trump is now invoking a well-worn theme,claiming once again that mail-in ballots will lead to widespread voter fraud. He insists that in West Virginia people are"selling the ballots,they're being sold,they're being dumped in rivers".

"This is not going to end well,"he claims.

"They found some with the name'Trump'just the other day in a wastepaper basket;they're being sent all over the place.... This is going to be fraud like you've seen."

Wallace doesn't intervene so he's able to continue. It's a theme that Trump has been pushing for months,which critics say is designed to delegitimise the election,should Biden win.

Just last week the US President declined to commit to a peaceful transfer of power if he loses the November 3 presidential poll.

"We're going to have to see what happens,"Trump said at a news conference,responding to a question about whether he’d commit to a peaceful transfer of power."You know that I've been complaining very strongly about the ballots,and the ballots are a disaster."

We're now onto the issue of election integrity. As this debate takes place,millions of Americans are getting mail-in ballots,providing them with an option for postal voting in the era of coronavirus.

Asked by Wallace what he's prepared to do to reassure the American people that the next president will be the legitimate winner of the election Biden says that,as a first step,people must be able to vote as they see fit - either by mail,or safely at the ballot box.

This would mean ensuring polling services are well resourced and remain open for as long as necessary,he says.

"You will determine the outcome of the election,"says Biden."Vote,vote,vote early... and if you're able to,vote in person."

Trump is still ducking the question of climate change,saying it may exist “to some extent” but returning to his claim that US forest fires are caused by land management rather than climate change. He is also arguing in support of his moves to strip away Obama-era fuel standards. California is ignoring Trump and has responded by announcing that it will simply phase out internal combustion engines.

Biden by comparison is happy to focus on this issue. He is campaigning on a US$2 trillion ($2.8t) green stimulus recovery and in the debate just observed that there would be no new oil or coal power stations. In this most major energy consultancies agree.

He is clearly happy to stand by these policies,emphasising that he would rejoin the Paris agreement and use American diplomatic might to encourage other countries to do more.

Trump has falsely claimed that Biden’s environmental plan would cost US$100 trillion. Trump appears to be discussing the so-called Green New Deal,proposed by elements of the left of the Democratic Party rather than Biden’s own plan. At the end of a long answer,Biden noted the cost of climate change on the economy.

Trump is really going for the jugular here,attacking Joe Biden's son Hunter (again) for discredited claims over his dealings in Ukraine.

As Joe Biden starts talking about his other son Beau,who died of cancer in 2015,Trump hits out at Hunter personally,bringing up his previous cocaine use.

Biden does well not to take the bait too much,noting that Hunter did have an addiction - like many other Americans.

'My son,like a lot of people,had a drug addiction,"he says."He's fixed it,he's worked on it,and I'm proud of him."

As expected,the President's aggressive style and personal attacks have so far allowed him to dominate his opponent.