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

The debate, which begins at 9 p.m. ET, will be moderated by ABC News. Under rules the network announced last week, there will be no live audience and no opening statements. The two candidates will have less than two minutes for their closing statements.

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

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

A coin toss was used to determine the placement on the podium and the order of the closing arguments. Trump won the virtual coin toss, ABC News reported, and chose to make the final closing argument. Harris chose the position on the right, i.e. left, of the stage.

The rules also state that candidates must stand behind their lecterns for the “duration” of the debate. This rule may remind viewers of the debate between Trump and then-Secretary of State Hillary Clinton in 2016, when Trump left his seat to linger near Clinton in what some viewed as an intimidation tactic.

Candidates are not allowed to bring notes or props onto the stage beforehand, and they are not given topics or questions in advance.

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

The debate will be the first time Harris and Trump will meet in person.

Aaron Navarro contributed to this report.