Explained | All you need to know about the Harris-Trump presidential debate

US Republican candidate Donald Trump and his Democratic rival Kamala Harris will square off next month in their first presidential debate since President Joe Biden quit the race.

It will be the first chance some 240 million US voters get to hear Trump and Harris explain their policies side by side ahead of the November 5 election, and a rare moment when the two are in the same room.

Here are some details about the highly anticipated event:

When and where is the debate?

The debate, hosted by ABC News, will take place on September 10 at 9 pm EDT (6.30 am IST, September 11) in Philadelphia, Pennsylvania, in one of the battleground states that swing between Democrat and Republican and will help determine the winner of this year's election.

The debate will be held at the National Constitution Center, a museum devoted to the US Constitution in Philadelphia's Independence Mall, which also contains the Liberty Bell and Independence Hall.

How can you watch the debate?

Moderated by ABC's David Muir and Linsey Davis, it will air on ABC and stream on ABC News Live, Disney+ and Hulu.

It will also be produced in conjunction with local Philadelphia network WPVI-TV, an ABC affiliate.

What are the ground rules?

The candidates' microphones will be muted when it is not their turn to speak. The Harris campaign agreed to this rule on Wednesday after weeks of back-and-forth with the Trump campaign, with Harris' team initially hoping for so-called "hot mics" throughout the debate and Trump's team pushing for muted mics.

CNN's June debate between Biden and Trump also had muted microphones when candidates were not speaking. The CNN debate also banned any props, had no live audience and included two commercial breaks, conditions that are expected to be replicated.

What's expected of Harris?

Harris will be entering the debate with momentum. After she closed out the Democratic National Convention in Chicago on Aug. 22, her campaign announced she had raised more than $500 million since entering the race.

She has surged in polls. Polling aggregator website FiveThirtyEight showed Harris up by 3.5 percentage points in national polls but much tighter races in some battleground states.

Voters want to hear more about her policy plans, strategists say. She may attack Trump on his appointment of three Supreme Court justices who helped overturn Roe v. Wade, mention "Project 2025," a sweeping conservative policy framework written by some of his closest advisors, and contrast her record as a prosecutor with his felony conviction.

Harris, who launched a short-lived White House bid in the 2020 election cycle, has tried to portray herself as both an extension of the Biden administration and the face of a new generation, and is likely to detail her personal story and middle-class upbringing.

What's expected of Trump?

Trump has struggled to find a coherent and effective line of attack on Harris since she entered the race. He has accused her of being a radical leftist while also suggesting she bears responsibility for Biden’s more centrist policy agenda. At times, he has questioned her intelligence and her biracial identity.

In his debate with Biden, Trump repeated familiar falsehoods that mostly went unchallenged. Harris is expected to be a tougher opponent and could put Trump more on the defensive over facts, policy and his conduct following the 2020 election. Trump could fall back on personal attacks if flustered.

Trump likely will to try and pin issues that helped sink Biden’s popularity with voters on Harris – inflation and border security – while suggesting she’s not ready to be the nation’s commander in chief. He may bring up the liberal stances she took as a 2020 candidate and could attack the Biden administration's record in Gaza and Ukraine.

At the same time, Trump has to reassure skeptical voters he has the temperament to regain the job he lost four years ago. The last time he faced a woman candidate, Hillary Clinton in 2016, he physically hovered behind her in one debate and referred to her as “the devil” and a “nasty woman.”

What other topics are likely?

The economy, particularly high consumer prices, is likely to be a main topic.

Trump has touted plans on taxes and health. He has also proposed ending taxes on tipped income, a proposal Harris has adopted, which could mean a chance for the two to discuss a rare shared interest.

What about third parties?

Vice President Harris, who secured the Democratic nomination after Biden stepped aside last month following a disastrous debate performance, said in early August she would participate in the Sept. 10 debate previously agreed to by Biden and former President Trump.

Trump, 78, and Harris, 59, will not be joined by third-party candidates. The deadline to qualify was September 3, and qualifying candidates had to appear on a sufficient number of state ballots and reach at least 15 per cent support in four national opinion polls that meet ABC's standards.