Harris and Trump debate in Philadelphia Tuesday night. Here’s what you need to know

Here’s what you need to know about this second debate of the 2024 presidential election cycle.

When and how to watch

The event will air at 9 p.m. ET for 90 minutes from the National Constitution Center in Philadelphia. ABC News anchors David Muir and Linsey Davis are slated to moderate the debate, which will be broadcast by the network and streamed on ABC News Live, Disney+ and Hulu.

Follow NPR's live blog for the latest updates, analysis, fact-checking and color; listen to NPR’s special coverage of the ABC News Presidential Debate Simulcast on many public radio stations.

What are the rules for the debate?

The debate rules echo those agreed on for the June matchup. That means microphones will once again be muted unless a candidate is speaking, something the Harris team asked to change for this debate.

It’s a rule initially proposed by the Biden campaign ahead of the first debate and was largely seen as a potential shake-up to Trump’s typical debate style. Instead, it ended up benefiting the former president, who has a history of interrupting in these settings to the point of his campaign’s detriment. Instead, the technical change helped Trump appear more controlled.

Harris’ campaign told ABC that Harris would be disadvantaged by the muted mics because it would shield Trump from direct exchanges — but said that it would agree to the terms lest Trump drop out of the debate altogether.

A campaign official, speaking on condition of anonymity to describe private negotiations, said that a pool would be on hand to hear what the candidates are saying into muted microphones — and that if there is “significant crosstalk,” the network may unmute both microphones. The moderator will warn candidates to stop frequent interruptions, the official said. “Our understanding of these things helped inform our decision to accept muted mics,” the official said.

There will be no audience and candidates will not be permitted to question each other directly. In addition, neither will be allowed to bring pre-written notes or props onto the debate stage.

What to watch for

Harris has mostly campaigned from the trail in her brief time as a presidential contender — excluding a single sit-down interview with CNN at the end of August. She has also struggled in the past with unscripted moments as vice president, which will put the spotlight on her ability to perform in a debate while also laying out some of her platform and going on the offensive against Trump.

Harris has been putting an emphasis on protecting reproductive rights while campaigning, and she’s likely to address it Tuesday night. Leading up to the debate, the Harris-Walz campaign launched its “Fighting for Reproductive Freedom” bus tour, pledging to make 50 stops in key states around the issues of abortion, IVF and reproductive rights.

Trump’s stance on this issue has been muddy. He’s made comments on abortion that appear to clash with some of his past views and statements while president. Recently, he acknowledged that Florida’s six-week ban was too restrictive, then clarified shortly after that he would not support the state’s upcoming ballot measure that, if passed, would safeguard access to abortions up until fetal viability.

Trump is likely to link Harris to Biden’s handling of the economy and immigration, two areas where Republicans have heavily criticized the White House. He may also highlight aspects of her political record, including her past support for decriminalizing border crossings and banning fracking — two policies she backed during her 2020 presidential bid and has since pivoted on.

On the other hand, Harris has repeatedly tied Trump’s platform to Project 2025, a 900-page set of policy proposals for a potential second term put forward by a conservative think tank, The Heritage Foundation. Trump has tried to distance himself from the plan — which includes further restrictions on abortion access among a slew of moves that would increase executive power. 

Tuesday’s matchup also poses new stakes for Trump: He’s facing a very different opponent.

In the aftermath of the June debate, the former president’s mistakes weren’t a focus, largely because of Biden’s more noticeably poor performance. That said, Trump by no means had a perfect night, repeatedly highlighting false and misleading information. So this time, as NPR’s Domenico Montanaro pointed out, “If Harris has a solid debate, the focus could be on Trump in a way he doesn’t want.”

What's next?

Vice presidential candidates Minnesota Democratic Gov. Tim Walz and Ohio Republican Sen. JD Vance will face off on Oct. 1 in a debate hosted by CBS News. The two hold similar roles in their respective campaigns: to appeal to voters in the "Blue Wall" states of Pennsylvania, Michigan and Wisconsin this fall.

It’s unclear whether Harris and Trump will debate a second time. No additional dates have been formally announced.

NPR White House Correspondent Tamara Keith contributed reporting.