ATLANTA You may think weve been here before and we have.

President Joe Biden and former President Donald Trump are facing off Thursday night in their first debate of the 2024 presidential campaign. Theyve done this before, of course, four years ago, but things are different now.

Biden is the White House incumbent, and Trump is the Republican challenger and both are now in the position of having served in the job theyre seeking from voters in November. Theres no longer a global pandemic that makes in-person campaigning, as well as debating, logistically challenging, and even dangerous . Biden has since turned 81, while Trump isnt far behind, at 78. And Trump has become the first former president to be convicted of a felony as he faces a possible prison sentence.

All of these factors will make for a historic meeting of the two presumptive nominees, set to begin airing at 9 p.m. Eastern time on CNN . Heres what to know going into the debate.

1. Its the first, and possibly last, time they debate.

Biden and Trump last month agreed to two debates before Election Day: Thursdays event, which comes unusually early in the election cycle, and another debate set for Sept. 10, several weeks before the election. (It was the desire for this specific timing that prompted the campaigns to forgo working with the nonpartisan Commission on Presidential Debates .)

But depending on what happens at the former presidents sentencing hearing next month on his 34-count conviction for falsifying business records, theres the possibly Trump might be behind bars before the next debate. In that case, debating Biden might be the least of Trumps concerns if hes confronting the reality of accepting the Republican Party s nomination and possibly even governing from prison.

It also raises the stakes of Thursday nights meeting, less than five months from the election, if this ends up being the last time they appear together on stage. The candidates are under more pressure to make a lasting impression that sets the tone for the campaign through the remainder of the summer and into fall.

2. Its (mostly) just Biden and Trump in the room.

The two candidates agreed to have no live audience in the room when they meet at CNNs Atlanta studio. The room will be virtually empty except for the candidates and debate moderators Dana Bash and Jake Tapper.

Its the first time since the 1960 debate between John F. Kennedy and Richard Nixon that two presidential candidates have debated without a live audience. The unusual setup makes it so the candidates cant play to an audience or use them as a distraction. Biden and Trump have also agreed to mic muting when its not their turn to speak.

The media, meanwhile, will be watching the debate from an indoor arena at the Georgia Institute of Technology. The arena, nicknamed the Thrillerdome , is normally home to the schools mens and womens basketball teams but is being taken over this week by hundreds of out-of-town reporters.

3. Biden went into the debate highlighting Jan. 6 ...

Biden has already used the debate to remind voters about the Jan. 6, 2021, attack on the U.S. Capitol that Trump instigated at his Stop the Steal rally that morning, as Congress met to certify the electoral vote.

On Wednesday, the campaign rolled out an endorsement from Republican Adam Kinzinger, the former House member who declined to run for reelection after voting to impeach Trump for inciting the Jan. 6 riot. It also introduced a new ad with a Michigan sheriff who criticized Trump for sitting idly by while his supporters ransacked the Capitol in an attempt to stop Biden from taking office.

The campaigns blitz reinforces key Biden arguments against Trump: that hes a threat to democracy and that another Trump term would plunge the country back into the chaos of his first term.

4. ... while Trump demanded drug tests.

In the days and weeks leading up to the debate, Trump has vacillated between calling Biden a formidable debater and speculating that Biden will take some type of performance-enhancing drug ahead of their meeting. (Bidens campaign has called Trumps drug musings obviously false lies and desperate. )

Trump ramped up his attacks on Biden over the weekend in Philadelphia, predicting Biden would take a shot in the ass to get jacked up for the event. On Tuesday, Trump called on Biden to take a drug test and said he would submit to one as well .

The former president cant seem to make up his mind whether Biden is a skilled debater or a doddering puppet who cant make it through a 90-minute debate without drugs, though both attacks serve the purpose of lowering expectations for Trumps performance.

5. Trump and Biden are tied in polls.

The debate comes at a time when the two candidates are locked in a dead heat in national polling averages, with Trump ahead by a hair but still well within the margin of error months ahead of any votes being cast.

No survey taken this early in the election cycle is meant to reflect what will happen in November. But election forecasters see a general trend of polling weakness for Biden in some battleground states where voters are most concerned about the economy, border security and immigration.

Debates can give candidates a small polling bump, but its unlikely that whatever happens Thursday night will be enough to sustain that long-term.