Harris vs. Trump debate tonight (9/10): What you need to know

Former President and Republican nominee Donald Trump will face Vice President and Democratic nominee Kamala Harris in what could be a campaign-turning debate on Tuesday in a tight presidential race.

With nearly every poll within the margin of error and swing states threatening to be decided by just a handful of votes, the stakes are high as Harris introduces herself to a good portion of the electorate and lays out her agenda, while Trump tries to convince voters that he deserves another term after being voted out in 2020.

At 78, Trump is mounting his third run for the Oval Office as the oldest presidential candidate in history.

Voters already have seen how a debate can change the course of history: After a dismal debate performance against Trump in June, President Joe Biden dropped out of the race and endorsed Harris, who has electrified the Democratic base and built a coalition that includes many independents and Republicans while erasing a substantial lead Trump had held on Biden.

Still, the race is neck-and-neck and, with less than two months remaining until election day, could swing either way, depending on the debate.

How to watch the debate

The debate, which will take place at the National Constitution Center in Philadelphia and air on ABC, will be moderated by David Muir and Linsey Davis. The debate will start at 9 p.m. Eastern and last for 90 minutes with two commercial breaks.

Viewers can watch without cable via livestream on Disney+ and Hulu.

Also:

— NBC News will stream the debate at NBCNews.com and on the NBC News app. You can also watch for free on NBC News Now via YouTube and Samsung TV Plus.

— PBS News will livestream on its PBS News YouTube channel.

— The UK’s Sky News will stream on its YouTube account.

— Fox News will stream live via its YouTube account.

Some networks will also be streaming live on their social media accounts such as Facebook, TikTok or X.

What are the rules?

After some haggling between the Harris and Trump campaigns and ABC News, both campaigns have agreed to the rules.

The moderators will be the only ones asking questions, and the candidates will not be allowed to ask each other questions.

The most contentious issue had been whether a candidate’s microphone would be muted while their opponent is speaking. While the mics were muted in the Trump-Biden debate, Harris’ campaign had pushed for the microphones to be live at all times. They wanted her to interject and Trump to be heard if he tries to talk over her.

But the mics will be muted when the other candidate is speaking.

Each candidate will have two minutes to answer a question and two minutes to respond to the other candidate. They will also have an additional minute for “follow-ups, clarifications, or responses,” the rules state.

The debate will begin immediately with questions. There will be no opening statements. The candidates will be given time for a two-minute closing statement.

Like the June debate, there will be no audience.