NEW YORK — President Joe Biden begins 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 June 27. 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 and ever confident, will stay on the campaign trail before going to his Florida estate next week for two days of private meetings as part 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.

Pressure on Biden

The ground rules for the June 27 debate, the first of two scheduled meetings, are unusual.

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 podium to the viewer’s right, while Trump would deliver the final closing statement.

The next debate won’t be until September. Any stumbles June 27 will be hard to erase or replace quickly.

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, 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 punchier 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 “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.

But while some Democrats project confidence, Biden's allies also say he has spent much of the last two weeks traveling — in Europe and on the West Coast — limiting his ability to prepare. Others note incumbent presidents typically struggle in the season's opening general election debate.

Messina made both points even as he sought to play up the political stakes for Trump. He suggested Trump was taking an unnecessary political risk by debating Biden.

“I wouldn’t have done the debate if I was him,” Messina said of Trump. The strategist added, “Why would you want to give him this air? He decided he wanted to do this to knock him out, and if he doesn’t, then I think he’s in real trouble.”

Trump projecting confidence

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.

“Biden needs rehearsals with handlers to find some way to explain this mess he’s made of our nation,” Trump spokesman Brian Hughes said. "President Trump is always prepared to present to Americans his record of success and Biden’s weakness and failures.”

Biden’s camp is aware Trump will likely focus on his son Hunter, as the then-president did on the debate stage four years ago. Hunter Biden was recently convicted on three felony charges related to the purchase of a gun while allegedly being addicted to drugs. Republicans have also criticized Hunter Biden's foreign business dealings when Joe Biden was vice president.

Biden’s allies are also concerned, however, their famously combative rival might be on good behavior.

“For both campaigns, the goal here is reaching an audience of moderate, independent, swing voters in swing states who will, in many ways, be the deciding factor in this election,” said former Biden administration official Bill Russo.

“Trump has kind of a golden opportunity here. If he can pretend that he’s a reasonable human being for 90 minutes while he’s in the spotlight, he’s got a lot to gain,” Russo added. “The real key here is which Trump shows up.”