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

Harris and Trump square off Tuesday at what could be their only presidential debate, setting high stakes for an event expected to be viewed by millions of Americans and a key sliver of undecided voters. Here’s what to look out for.

Can Trump stay focused on policy? Staying on message on his four-year economic record is key, while veering into personal attacks would be counterproductive, allies told ABC News.

Harris has dual goals: make the case for herself as someone who would be a capable president and get under Trump's skin. How will she introduce herself to undecided voters?

Read the rest of the five things to watch for in the debate here.

Gov. Tim Walz, Harris' running mate, previewed the vice president's upcoming debate with Trump in a fundraising email on Tuesday morning -- contrasting their campaign's message on the economy and freedom with Trump's platforms.

"She's going to show everyone watching what this movement is all about: supporting families like yours and mine and building a future where everyone has the opportunity not just to get by, but to get ahead," the email reads. "Donald Trump is sure to talk about his twisted version of freedom," Walz claimed in the email.

-ABC News' Isabella Murray

Harris and Trump will have a handful of surrogates representing them in the spin room following the debate.

Harris will have Govs. Josh Shapiro of Pennsylvania, Gavin Newsom of California, Roy Cooper of North Carolina and Michelle Lujan Grisham of New Mexico representing her in the spin room post debate, a campaign official confirmed to ABC News.

In addition to attending a watch party hosted by the Trump campaign, GOP vice presidential nominee Sen. JD Vance will also participate in the spin room.

Robert F. Kennedy Jr., Gov. Doug Burgum, tech entreprenuer Vivek Ramaswamy, Sen. Marco Rubio, Rep. Bryon Donalds, and Sen. Rick Scott are also expected to appear on behalf of Trump.

-ABC News’ Fritz Farrow, Gabriella Abdul-Hakim, Will McDuffie, Kelsey Walsh, Lalee Ibssa, and Soo Rin Kim

House Republican Conference Chair Elise Stefanik teed up her expectations for tonight's presidential debate, telling reporters that Harris "cannot hide forever."

"Tonight at the debate, the country will finally get to see the stark contrast between the strength and success of President Trump's America-first policies and the devastation and weakness of Kamala Harris's radical, failed, far-left agenda," Stefanik, the fourth-ranked House Republican, claimed at a news conference in the Capitol Tuesday morning.

-ABC News' John Parkinson