LAS VEGAS – Vice President Joe Biden will watch the first Democratic debate not from behind a podium on stage here Tuesday, but from his home in Washington as five candidates face off for the first time.

The two front-runners and three underdogs will have two hours to make their case live on CNN, in front of a studio audience of 1,300 and millions more at home. Front-runner Hillary Clinton will be center stage, with chief rival Bernie Sanders to her right, and to her left Martin O’Malley, who needs a breakout moment tonight. They will be flanked by Jim Webb and Lincoln Chafee, both of whom are barely campaigning and will have to struggle for relevance.

After the debate, their surrogates will head to the “spin room” to sell their candidates. Clinton brought an entourage of Democratic elected officials, including New York Sen. Kirsten Gillibrand, former Los Angeles Mayor Antonio Villaraigosa and Reps. Sheila Jackson Lee, Judy Chu, and Dina Titus, who represents Las Vegas, according to placards in the spin room.

view photo essay 'Sin City' sets the scene for Democrats' first 2016 debate The Wynn Las Vegas sets the scene Tuesday for the first Democratic presidential debate of the 2016 election cycle — a veritable political fight night.

The lineup is a show of strength from the Clinton campaign, and a reminder that most of the Democratic party’s leadership has lined up behind her. Sanders, by contrast, will offer his senior staff and former MSNBC host Ed Schultz in the “spin room.”

O’Malley will have a former Democratic Party chair in his home state of Maryland. Chafee will have staffers, and Webb’s surrogates are to be determined.

Each candidate will have two minutes to make opening remarks before fielding questions from CNN anchor Anderson Cooper, who will be backed up by Dana Bash and CNN Español’s Juan Carlos Lopez. The podiums are just 20 inches apart and they’ll have 30 seconds to respond if a candidate mentions their name.

Aides to the candidates say they will not refrain from drawing contrasts with each other, but say their primary focus is to introduce their candidates to a larger audience.

Clinton spent the day holed up preparing for the debate, holding no public events and declining to walk through the debate hall before the main event. Instead, her aide Huma Abedin inspected the center podium, taking plenty of pictures.

Clinton’s husband, former President Bill Clinton, is in Las Vegas with his wife, but aides say he will not be in the room and will watch the debate on TV.

Your Democratic field. pic.twitter.com/eaPLDt0Zp9 — Alex Seitz-Wald (@aseitzwald) October 14, 2015

Meanwhile, Sanders’ aides finally convinced him to do some mock debates at his hotel Monday night, with his chief of staff playing Clinton and a consultant playing O’Malley. Sanders has little patience for the theatrics of politics and has resisted traditional debate prep. An aide noted he has plenty of material, citing Sanders’ eight-hour 2010 filibuster on the Senate floor.

O’Malley, the former governor of Maryland and a member of a Celtic rock band, will bring his guitar to the greenroom, according to an aide, though she declined to specify why. Chafee planned to go on a walk, an adviser said.

Sanders’ campaign claims they have organized more than 4,000 debate watch parties across the country, including one in the hotel just outside the debate. Clinton supporters will also gather to watch the debate.

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Correct the Record, a super PAC that coordinates directly with the Clinton campaign, will be ready to respond to what they view as attacks on Clinton from the moderators or opposing candidates, but say they will not take on the front-runner’s rivals by name.

NBC News’ Alex Jaffe contributed.