“His biggest issue that he had to prove to the American people was that he had the energy and the stamina, and he didn’t do that. So I think that is of concern.”

The performance was particularly startling as Biden had spent several days hunkered down at Camp David, the presidential retreat in Maryland, where mock debate sessions were held in a movie theatre on the property with 16 advisers.

Trump took a less structured approach, engaging in what his team described as “policy discussions” ahead of the debate, in between campaigning. He also claimed without evidence that Biden would need performance-enhancing drugs, or even cocaine, to enhance his performance and suggested they should both take drug tests for the debate.

To prevent a repeat of the chaotic first presidential debate of 2020, which was viewed as a debacle after Trump heckled and talked over Biden more than 100 times, microphones were muted so that candidates could answer relatively uninterrupted.

But the format seemed to suit Trump, who didn’t take long to start attacking a raspy-voiced Biden over his key vulnerabilities, including the crisis at the US-Mexico border, cost-of-living pressures in America and violent crime.

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“If he wins this election, our country doesn’t have a chance,” Trump said. “We probably won’t have a country left any more; that’s how bad it is. He is the worst in history by far.”

At one point, Trump also heckled the president, saying in response to an answer: “I really don’t know what he said at the end of that sentence. I don’t think he knows what he said either.”

Biden’s performance improved in parts, particularly when Trump was asked by CNN moderator Dana Bash if he would accept the results of November’s election, regardless of who wins.

“If it’s a fair and legal and good election, absolutely,” he said after trying to evade the question.

Biden replied: “I doubt you’ll accept it because you’re a whiner. When you lost the first time, you continue to appeal and appeal to courts all across the country. Not one single court in America said any of your claims had any merit but you continued to promote this lie.”

Foreign policy was also on the agenda. Trump refused to commit to a two-state solution to resolve the conflict between Israel and Palestine, and he accused Biden of sending America into expensive wars.

On abortion, Trump vowed he “will not block” access to abortion pills, while taking credit for the Supreme Court’s decision to overturn Roe v Wade, which until then had given women in America constitutional access to abortion.

“What happened is, we brought it back to the states, and the country is now coming together on this issue,” Trump said. “It’s been a great thing.”

And on the economy, Biden sought to paint himself as a champion for middle-class and working-class voters, touting his administration’s efforts to crack down on corporate greed, rein in prescription drug prices and reduce other cost of living pressures.

But it was not enough to halt the Democratic panic, or the glee of Trump’s campaign.

“Tonight, president Trump delivered the greatest debate performance and victory in history to the largest voter audience in history,” spokespeople Susan Wiles and Chris LaCivita said in a news release.