By Jeff Mason and Joseph Ax

WASHINGTON, Sept 29 (Reuters) - President Donald Trump and his Democratic challenger, former Vice President Joe Biden, meet in Cleveland on Tuesday for the first of three debates ahead of the Nov. 3 election, when Trump is seeking a second term in office.

Here are takeaways from the Tuesday night matchup:

GUEST LIST

Presidential candidates invite guests to debates with a calculated purpose: to emphasize a core campaign theme.

Ann Dorn, whose retired police officer husband was killed amid anti-racism protests in St. Louis in June, is among Trump's guests, a month after appearing in a video on his behalf at the Republican National Convention. Trump has hammered away at a "law-and-order" message in response to widespread civil unrest over police brutality and racism and accused Democrats of failing to support law enforcement.

Another Trump guest is former New York Mayor Rudy Giuliani, who played an integral role in trying to find dirt on Biden's son Hunter and his business dealings in Ukraine. Although the effort helped lead to Trump's impeachment, Giuliani's presence lends credence to reports that Trump intends to attack Hunter Biden anew at the debate.

Biden's guests include Kristin Urquiza, whose father, a Trump supporter, died of the coronavirus after dismissing its deadliness. The former vice president has sought as much as possible to turn the campaign into a referendum on Trump, and specifically on his handling of the outbreak, which has killed more than 205,000 Americans.

Biden's other guests included two local residents: Gurnee Green, a small-business owner, and James Evanoff, a steelworkers union member, who both represent the working families Biden is fighting for, his campaign said.

(Reporting by Jeff Mason in Washington and Joseph Ax in Princeton, New Jersey; Editing by Scott Malone and Peter Cooney)