Former President Donald Trump and Vice President Kamala Harris will meet for their first debate Tuesday at the National Constitution Center in Philadelphia in a showdown that could define the rest of the presidential campaign.

The debate, which begins at 9 p.m. ET, will be hosted by ABC News. There will be no live audience and no opening statements, according to rules the network released last week. The two candidates will have less than two minutes to deliver their closing statements.

Harris and Trump are not allowed to ask each other questions. Only the moderators — ABC’s David Muir and Linsey Davis — are allowed to ask questions.

The debate will last 90 minutes and will include two commercial breaks. The candidates will have two minutes to answer questions, two minutes for rebuttals and an additional minute for follow-ups and clarifications. As CBS News reported previously reportedHarris’ campaign team agreed to mute microphones when a candidate is not speaking.

A coin toss determined the podium position and the order of closing statements. Trump won the virtual coin toss, ABC News reported, and he chose to deliver the final closing statement. Harris chose either the podium right or podium left position.

The rules also state that candidates must remain behind their lecterns for the “duration” of the debate. This rule may remind viewers of a 2016 debate between Trump and former Secretary of State Hillary Clinton, when Trump left his spot to linger near Clinton. Some saw the move as an intimidation tactic.

Candidates are not allowed to bring pre-written notes or props onto the stage, nor are they given topics or questions in advance.

ABC is allowing other television networks to simulcast the debate. CBS News will air the proceedings on the CBS broadcast network and the streaming network CBS News 24/7.

The debate will mark the first time Harris and Trump have met in person.

Aaron Navarro contributed to this report.