The lineup for Thursday is as follows, from left to right: Marianne Williamson, a self-help author; former Gov. John Hickenlooper of Colorado; Andrew Yang, an entrepreneur; Mayor Pete Buttigieg of South Bend, Ind.; Mr. Biden; Mr. Sanders; Senator Kamala Harris of California; Senator Kirsten Gillibrand of New York; Senator Michael Bennet of Colorado; and Representative Eric Swalwell of California.

The candidates will stand in a tight semicircle on a debate stage at the Adrienne Arsht Center for the Performing Arts in Miami, surrounded by 600 square feet of screens that include a wraparound image of the White House. The lecterns are made of Plexiglas and carry the presidential seal. NBC, using five moderators, is hosting the debate.

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On the first night, Ms. Warren will have the largest target on her back, as the only candidate on stage who is polling in double digits. She will be surrounded by candidates in search of a breakout moment.

One of them, Mr. O’Rourke, is looking to stop his slide in the polls, which began shortly after his March campaign announcement. And Mr. Booker, who will stand on the other side of Ms. Warren, has yet to have a breakout moment.