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 tonight's debate, there will be a rush to anoint a "winner" and a "loser," but the only way we can really do that is once we have data on how the debate will actually affect people’s votes. To that end, 538 partnered with Ipsos to poll the same group of likely voters both before and after the debate to see how their attitudes change. Here are some of the key findings from our pre-debate poll, which was conducted using Ipsos' KnowledgePanel.

First, we asked respondents to rate how well they thought each candidate would perform in the debate tonight on a five-point scale. On average, Trump got a score of 2.96 out of 5, and Biden got a score of 2.58 out of 5. In other words, expectations are significantly lower for Biden tonight, which could end up helping him -- even a so-so performance from Biden would exceed most people's expectations.

It looks like the reason people have such low expectations for Biden is his advanced age. We also asked respondents to grade each candidate's physical, mental and emotional fitness on a five-point scale. On average, Biden got just a 2.3 out of 5 on physical fitness and a 2.4 out of 5 on mental fitness. Trump bested him on both of those measures, but Trump got only a 2.6 out of 5 on emotional fitness, which was lower than Biden's score.

We also asked voters what issues would have the most impact on their vote. Fifty percent ranked inflation or increasing costs as one of their top three issues, while 37% included immigration. Voters also said Trump would do a better job handling those issues than Biden, so it will be especially important for the president to show strength on these issues tonight.

Finally, we asked voters which candidates they were considering supporting. Heading into the debate, 44.8% of voters are at least considering voting for Trump, 44.5% are at least considering voting for Biden and 18.5% are at least considering voting for independent candidate Robert F. Kennedy Jr., who failed to qualify for the debate. (Respondents could say they were considering multiple candidates, which is why these numbers add up to more than 100%.) We'll ask voters the same question after the debate to see whether these numbers shift.

-538's Nathaniel Rakich