Trump campaign spokesperson Danielle Alvarez said Tuesday morning on ABC News Live that Trump "does not do traditional debate prep" and reiterated that he has been campaigning and engaging in policy discussions instead.

"I would say that the president does not do traditional debate prep. He's on the campaign trail constantly. We see him in key battleground states every week, joined by tens of thousands of patriots," she said. "We know that he does tough interviews, both nationally, locally."

"That's truly how he prepares for these debates, having those conversations every day. He's ready to step back into the White House," she continued. "We also know that he prefers to have those policy discussions, and he's been doing that with elected members in Congress like Matt Gaetz, with former Congress member Tulsi Gabbard and others -- very similar to what he did to prepare for that first debate against Joe Biden. He has prepared in a similar way again, just by getting out there and talking every day to voters and talking to media."

-ABC News' Soorin Kim, Lalee Ibssa and Kelsey Walsh

Just hours away from the debate, a campaign source is setting expectations that Harris is not "underestimating" Trump's ability to debate, and that it would be a "mistake" to do so.

The Harris team expects Trump to be "good" at debating, stressing that Trump has done this more than anybody else, while it will be Harris's first presidential debate.

The Harris campaign is "happy to get under [Trump's] skin," and they hope that bringing former Trump officials into the spin room later this evening will accomplish this.

On a campaign call last night, a source said Harris is ready for any version of Trump that shows up -- whether it's the presidential Trump, the more mellow Trump during the Biden debate or a more aggressive version.

-ABC News' Selina Wang

The consequential Harris-Trump face-off will air live tonight at 9 p.m. ET on ABC and stream on ABC News Live, Disney+ and Hulu.

ABC News Live is available on Samsung TV+, The Roku Channel, Amazon Fire TV devices, YouTube, Tubi, the ABC app, and ABC.com.

ABC News Digital and 538 will live blog the latest from the debate stage with coverage, analysis and fact checks.

SiriusXM users can listen to the debate on Channel 370.

The prime-time pre-debate special, "Race for the White House," will air at 8 p.m. ET and stream on ABC's platforms.

Read more here.

Harris and Trump are facing off at a pivotal time, with just weeks until Election Day and days before some states begin the early voting process.

Hot-button political issues that are likely to be discussed by Harris and Trump include the economy and inflation, immigration, reproductive rights, and crime and gun violence.

Foreign policy and the state of democracy are also expected to come up.

Read more here.

A recent New York Times/Siena College poll found a sizable share of likely voters (28%) and registered voters (31%) feel they need to know more about Harris as a candidate. Those numbers were even higher among independent voters: 41% of registered independents and 38% of likely voters who identified as independent said they needed to learn more about her.

Her campaign is well-aware that a large slice of the critical voting bloc feels they don't know Harris well enough, ABC News Chief White House Correspondent Mary Bruce reports.

Tonight, she'll want to fill in the blanks in what is her highest-profile appearance since her acceptance speech at the Democratic National Convention last month. But beyond that, their real goal is to make clear the stark choice in this election between what she wants to do as president and what Trump intends to do.