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

Tuesday night's highly anticipated presidential debate will take place at the National Constitution Center, just steps away from where the U.S. Constitution was drafted and signed in Philadelphia in 1787.

The center is a private, nonprofit organization that attracts people from all over the country and world to learn about, debate and celebrate the historic document, according to its website.

Ahead of the debate, the stage where Harris and Trump will spar was photographed with the opening words to the constitution's preamble brightly on it: “We the People.”

Lara Trump, co-chair of the Republican National Committee, said on CNN on Tuesday morning that Donald Trump has done "traditional debate prep," in addition to preparing by speaking to the media and attending public events.

"He has been preparing for this debate. He's done traditional debate prep," she said, before citing media appearances such as town halls, press conferences, podcasts and interviews.

The Trump campaign has previously focused on media and public events as Trump's debate prep, barely discussing more "traditional" debate prep.

Lara Trump framed her father-in-law's public events and media availability as a "stark contrast, of course, to what we've seen from Kamala Harris."

"I think Donald Trump is very focused on this debate tonight. He knows how important it is. He doesn't take anything for granted," she said.

– ABC News' Oren Oppenheim

Looking ahead to Tuesday night's debate, Vice President Kamala Harris tweeted "America, see you tonight."

Before departing for Philadelphia on Monday, Harris told reporters that she's feeling "good." She also gave a thumbs up.

The vice president's tweet also included a link to a list of debate watch parties the campaign is hosting across the country.

-ABC News' Fritz Farrow

Vice President Kamala Harris repurposed former President Barack Obama's suggestive dig at Trump over what Obama called his "weird obsession with crowd sizes" while speaking at the Democratic National Convention last month.

"Here's a 78-year-old billionaire who has not stopped whining about his problems …" Obama said in the clip used in the ad, just before a clip of Trump at rally plays.

"Ooh, she had a big crowd! Ooh, that crowd," Trump said in the snippet, mocking news reports about turnout for Harris.

"This weird obsession with crowd sizes... it just goes on, and on, and on," Obama says as the ad returns to him, followed by shots of small Trump crowds and sounds of crickets chirping.

"America's ready for a new chapter. We are ready for a President Kamala Harris," Obama says.

The Harris campaign said the ad, titled "Crowd Size," will air on Fox News the day of the debate because "Trump is known to watch" the network.

The 30-second ad is set to air nationally on cable news and in local West Palm Beach and Philadelphia markets.

– ABC News' Fritz Farrow, Gabriella Abdul-Hakim, and Will McDuffie