NEW YORK — President Joe Biden began an intense period of private preparations Friday at Camp David for what may be the most consequential presidential debate in decades.

The 81-year-old Democrat’s team is aware he cannot afford an underwhelming performance when he faces Republican rival Donald Trump for 90 minutes on live television Thursday. Biden’s team expects aggressive attacks on his physical and mental strength, his record on the economy and immigration and even his family.

Trump, 78, will stay on the campaign trail before going to his Florida estate next week for two days of private meetings as part of aides say is more of an informal prep process.

The ex-president’s allies are pushing him to stay focused on his governing plans but expect him to be tested by pointed questions about his unrelenting focus on election fraud, his role in the erosion of abortion rights and his unprecedented legal baggage.

The CNN debate will be full of firsts, with the potential to reshape the presidential race. Never before in the modern era have two presumptive nominees met on the debate stage so early in the general election season. Never before have two White House contenders faced off at such advanced ages, with widespread questions about their readiness.

And never before has a general election debate participant been saddled with a felony conviction. The debate stage meeting comes just two weeks before Trump is scheduled to be sentenced on 34 felony counts in his New York hush money trial.

“You can argue this will be the most important debate, at least in my lifetime,” said Democratic strategist Jim Messina, a 54-year-old who managed President Barack Obama’s 2012 campaign.

Adding to the pressure are the ground rules for next week’s debate, the first of two scheduled meetings.

The candidates agreed to meet at a CNN studio in Atlanta with no audience. Each candidate’s microphone will be muted, except when it’s his turn to speak. No props or prewritten notes will be allowed onstage. The candidates will be given only a pen, a pad of paper and a bottle of water.

There will be no opening statements. A coin flip determined Biden would stand at the lectern to the viewers’ right, while Trump would deliver the final closing statement.

Biden arrived at Camp David on Thursday night and is expected to hunker down with senior campaign aides until the debate. While traveling to the mountainside retreat in Maryland, he gave a thumbs up to reporters when asked how debate prep was going.

The president’s aides have been reluctant to share details about his preparations, run by former chief of staff Ron Klain. But they’ve signaled he’s preparing to be aggressive and wouldn’t shy away from using the term “convicted felon” to describe his opponent.

One adviser not authorized to speak publicly about debate strategy noted Biden has been increasingly pointed in recent remarks about Trump and plans to carry that theme through to the debate. That’s still while trying to project himself as the “wise and steady leader” in contrast with Trump, the adviser said.

Among some political operatives, there’s the sense Biden may have more to lose given his struggle to generate momentum amid signs of weakness within his political coalition. Trump and his allies have set an extraordinarily low bar, however, by suggesting for months Biden is contending with serious physical limitations that make it difficult for him to stand for 90 minutes or string together two sentences.

“It’s like the mirror test. Put a mirror under Biden’s nose, and if it fogs it up, he wins, right? That’s about what the threshold is for Biden,” Republican strategist and Trump ally David Urban said with a laugh. “Can Biden demonstrate that he’s mentally nimble? That’s the big question.”

Yet Trump sought to shift expectations in a Thursday interview with “The All-In Podcast,” in which he veered sharply away from his typical Biden taunts. He said Biden “destroyed” vice presidential nominee Paul Ryan in their 2012 debate.

“I assume he’s going to be somebody that will be a worthy debater,” Trump said of Biden. “I don’t want to underestimate him.”

Biden’s aides have dismissed concerns about his age and mental readiness. They’re fighting against what they allege is deceptive editing of video clips to suggest he’s confused.

Trump’s team sees the faceoff as an opportunity to demonstrate a clear contrast with Biden’s leadership ability and governing record.

And while downplaying his preparations, Trump aides have a pattern of insisting he doesn’t prepare for debates when, in fact, he does — in his own way. Instead of mock debates with lecterns and stand-ins or hours spent poring over policy books, the ex-president is expected to rely on a series of conversations about policy and strategy with aides and political allies.

Trump will also make public appearances over the coming days.

On Saturday, he’s set to host a rally in Philadelphia and deliver a keynote address to a conference of Christian conservatives in Washington. He also has a fundraiser in New Orleans on Monday before going to his Florida estate for meetings.