Trump-Harris debate live updates: Candidates go on attack in zinger-filled showdown

In the most recent ABC News/Ipsos poll, Harris had an advantage over Trump when it came to who Americans think has better "physical health" and "mental sharpness" to serve effectively as president.

Trump has recently gotten attention for his rambling and often-incoherent speaking style, and while that's nothing new for him, this will be his first time directly facing a new opponent, who's nearly 20 years younger than him. Whether or not Trump's age or mental acuity come up explicitly in tonight's debate, how he handles himself — and how viewers respond afterward — could help him put some of those concerns to rest, or exacerbate them and give Harris an opening.

—538's Tia Yang

South Dakota Gov. Kristi Noem said Trump should hold Harris' feet to the fire on policy, referencing policies this campaign on things like fracking and health care that differ from stances she took during her 2019 run.

"He needs to hold her accountable to what she truly believes and what she's done when she was given more power in a bigger position," Noem told ABC News.

Noem added that accountability should be more focused on policy than personality, but added, "His personality always shines through, it just does, and she's going to have a tough time dealing with that."

-ABC News' Tal Axelrod

We're obviously going to hear about a lot of different issues tonight — and some of those issues will be comfortable ground for Trump, while others will be Harris' home turf. The latest ABC News/Ipsos poll asked Americans whether they trusted Trump or Harris more to handle 11 different issues. Harris was trusted more on six, Trump was trusted more on four, and one (crime and safety) was tied.

Harris also had the biggest trust advantage on any issue: 16 points, on both abortion and race relations. However, Trump was trusted more than Harris on the three issues that Americans usually say are the most important to their vote: the economy, inflation and immigration.

—538's Nathaniel Rakich

Members of the Trump family attending the debate with him tonight are his son Eric Trump and his son's wife -- and co-chair of the Republican National Committee -- Lara Trump, sources familiar with the matter tell ABC News. Melania Trump is not there.

On the plane with him from Florida to Philadelphia were Florida Rep. Matt Gaetz and former Democratic Rep. Tulsi Gabbard, who have been helping Trump with debate prep. Also on board -- one of his lawyers, Alina Habba, as well as senior staffers Chris LaCivita, Susie Wiles, Steven Cheung, Corey Lewandowski and Jason Miller.

Notably, controversial conservative media influencer Laura Loomer was also flying with Trump. Loomer has pushed multiple conspiracy theories about Harris, including racist and sexist attacks on the vice president.

-ABC News' Lalee Ibssa and Katherine Faulders