Inside Joe Biden's secret debate rehearsals ahead of next week's showdown with Donald Trump - and the biggest mistakes he could make

Joe Biden is locked in an intense five-day debate camp as he prepares to take on his hated rival Donald Trump in Thursday's televised brawl.

Trump is expected to goad, insult, interrupt, and heckle the president - and the man playing him in practice sessions won't take it any easier on Biden.

Bob Bauer, the president's longtime personal lawyer, is expected to stand in for Trump as he did before the successful 2020 debates.

Biden left for Camp David on Thursday night and will use the favorite presidential retreat for the ultra-secret debate preparation.

Such is the code of silence around debate camps that Bauer wouldn't even confirm he would reprise his role as the villain this time.

But he did share some behind-the-scenes details from the 2020 preparations, and a few of the mistakes he and Biden must avoid both in practice and on Thursday.

Bauer said he had to immerse himself in what the opposing candidate said, along with their tone and style of argument, to recreate the experience of debating them.

'I as Donald Trump, played my part lying and blustering and bullying my way through the mock sessions,' he wrote in his book, The Unraveling.

'To prepare, I watched hours of tapes of the 45th president, as a businessman, 2016 candidate, and then in office. 

'We set aside special sessions during which I was expected to be at my Trump-worst - as personally insulting and unhinged as Trump can be.'

The first rule, which is particularly important with Trump, is that he can't hold back in going after Biden in the nastiest possible way.

'You cannot be afraid of laying down on the table something that your candidate that you're preparing this for won't like,' Bauer told Politico.

'That could be something that's personally insulting. That's something that can be completely false about policy positions they've taken.'

Another big mistake is to use an argument that the opposing candidate could make, but never actually made before - as he did in 2020.

Bauer described how in a mock debate before the last election he had Trump effectively calling for Roe v Wade to be overturned.

He noted that Trump subsequently took credit for appointing judges that in 2022 did in fact strike down the 1973 precedent upholding the constitutional right to abortion, but that he hadn't done it by 2020. 

'That was a mistake. You want to avoid those kinds of mistakes because you don't want the candidate preparing for an argument that the candidate is not going to hear,' he said.

Biden aides said the president hoped to use the debate to hold Trump accountable for his role in helping overturn Roe v Wade.

Other candidates have in the past had their Trump double actually dress up as him, but Bauer said that was something he avoided.

'This is not a Saturday Night Live impression. You don't want to detract from the serious business of prepping the candidate,' he said.

Biden 2020 campaign aide Bill Russo said another mistake for Biden to avoid in the live debate was being lured in to a slanging match with Trump.

'I think the big challenge here is how do you make sure to call out the mistruths, the lies, the half-truths that you can expect Trump's going to be dishing out but without getting pulled into just playing on Trump's turf,' he told the Wall Street Journal.

Instead, Bernie Sanders's 2020 campaign manager Faiz Shakir predicted Biden would try to push Trump's buttons to make him look bad.

With the right prompting, he said, Trump would 'offend, upset and annoy the vast majority of Americans who already voted against him'.

Some campaign insiders were concerned using Bauer to play Trump meant Biden's team was playing it too safe.

'It's no surprise that Bauer is in prep again with most of the other usual suspects. Biden likes to have his security blanket around him,' one told the New York Post.

'This team knows how to handle him and how he wants to be handled for these exercises.

'Will they run debate prep like a Bravo reality TV show? Because they should.

'Will they be innovative and creative enough in prep to coach him to expect the unexpected and the unconventional? That's all that matters.'

The insider said Biden was the most experienced debater in American politics, and felt at home behind the podium - but needed to be creative this year.

'He'll be ready to spar over both of their records. But can the old dog be taught new tricks? Does Bob have the tricks and tools to teach a debate against such an unpredictable opponent?' they said.

Former White House chief of staff Ron Klain will oversee Biden's debate team in his fourth election cycle involved in the process.

Klain now works as an executive for Airbnb and will take time off to lead Biden's debate preparations.

The first debate, held in Atlanta and televised on CNN, will begin at 9pm on Thursday. About 73 million people watched the first debate in 2020.

Biden, who prefers briefing binders and practice sessions, will be focused on holding Trump accountable on his record and coming up with punchy one-liners to throw off the former president.

Trump, meanwhile, has been trying out new catch phrases and bits of rhetoric, ready to pound his rival with his words. 

He is not expected to do any mock debate sessions that would require someone to play the part of Joe Biden.

Next Thursday's debate in Atlanta is believed to be the first time the two men will be in the same room together in four years - since their final presidential debate on October 15, 2020.

The Biden campaign is already down playing expectations, noting the president has been busy with his day job instead of preparing for the debate stage. 

'The president will have less time for debate prep than 4 years ago given his day job, so prep will largely be confined to immediately prior,' a campaign official told DailyMail.com.

Biden is coming off a hectic two-week travel schedule, having spent five days in France for the 80th anniversary of D-Day and a state visit. He then went to Italy for 48 hours for the G7 conference. He spent the weekend on the West Coast fundraising. 

But the biggest hurdle the 81-year-old will have to overcome are the concerns about his age. 

Trump, meanwhile, also has been downplaying the upcoming showdown.

At a rally in Wisconsin this week, he argued he won't just be debating Biden but also CNN's two debate moderators - Jake Tapper and Dana Bash - whom he says doesn't like him.

'I'll be debating three people instead of one half of a person,' he said. 

The debate will last 90 minutes with two commercial breaks and Biden will get the first word and Trump will get the last.

The president will focus on attacking Trump for 'ripping away reproductive rights, promoting political violence and undermining our democratic institutions, and doing the bidding of his billionaire donors to fund tax giveaways to the ultra-wealthy and corporations by hurting seniors and the middle class,' a Biden campaign official said.

But neither man has held back in attacking his rival.

Trump claims Biden is physically and mentally unfit for office, while Biden has called his Republican rival 'unhinged' and a danger to democracy.

Biden's supporters also point to Trump's role in the January 6th insurrection at the Capitol, his attempts overturn the 2020 election and his conviction on May 30 for 34 felony counts for his involvement in a hush-money scheme to keep an alleged sexual encounter with a porn star from the public. 

Trump, meanwhile, could attack Biden's son Hunter, who was convicted last week on three felony charges related to a 2018 gun purchase.