For the first time since the first televised debate between John F. Kennedy and Richard Nixon in 1960, there will be no live audience at CNN's studio in Atlanta.

The candidates' microphones will be muted unless it is their turn to speak. They will have two minutes to respond to questions and one minute for rebuttals, and there will be a red flashing light to indicate to them their time is about to expire.

The 90-minute program will have two commercial breaks, but Trump and Biden won’t be able to consult with their teams during them. No props or note cards are allowed on stage.

Here's what experts said about the new rules, and how they may help or hurt each candidate.

Several possible vice presidential picks for Trump are in Atlanta for the debate.

Sens. Marco Rubio, R-Fla., Tim Scott, R-S.C., and J.D. Vance, R-Ohio, Rep. Elise Stefanik, R-N.Y., and former Housing and Urban Development Secretary Ben Carson were seen in a picture posted to X by Stefanik.

Trump has repeatedly teased an announcement of who will join him in the 2024 ticket, but he has yet to make a final decision.

Voters across Wisconsin, Michigan, Georgia and Pennsylvania spoke with ABC News about their unhappiness with both candidates and what they're looking to hear from them during the debate.

"I'd like to see what they're going to do for small businesses in this country," said Scranton resident Jennifer Merceau, whose husband owns a masonry company.

Janee Johnson, who works at Toast 'N Jams in Muskegon, Michigan, said the focus should be on doing the "right things for America."

Michael Kordecki, the owner of that restaurant, wishes he could tell the candidates to "be more positive about America, about our future, and about what we can do with or without new people coming into the country."

Read more about these voters here.

With 131 days until Election Day, this faceoff is occurring months ahead of the usual fall timeline.

"The combination of having so many people with doubts about both candidates, coupled with the first debate occurring before either convention, heightens its potential importance," Republican political strategist Whit Ayres told ABC News.

Veteran Democratic strategist James Carville told ABC News: "People's attitudes are very fixed and voters tend to be pretty entrenched. The person that 'wins' ... in this debate is going to be the one that provides voters with some new information."

-ABC News' Isabella Murray and Tommy Barone

After a stifled and stumbling opening statement, Biden has had some good replies to Trump when talking about policy -- especially on abortion and Jan. 6. But that will be little comfort for his campaign, which is fighting hard against the impression that Biden is too old to hold office. In a 538/Ipsos poll of Americans released today, 40% of Americans said they rated Biden's mental fitness to be president as "terrible," compared to 35% for Trump -- and fewer Americans rate him positively for his physical fitness to lead, too.

538's election forecasting model currently gives Biden and Trump each a 50-in-100 chance of winning the election. Biden's initial impression could prevent him from making sizable gains over those numbers, despite the rest of his performance.

-538's G. Elliott Morris