The first Democratic presidential debate will feature front-runner Hillary Clinton, socialist firebrand Bernie Sanders and a trio of guys most Americans do not know.

The contest is set for Tuesday at 8:30 pm EDT in Las Vegas and will be aired on CNN. It is slated to last two hours. The Republican debate last month went long, hitting three hours, but this show doesn’t have the star power of Donald Trump, so 120 minutes will do.

Americans will finally have a chance to see Clinton and Sanders — who have been shadowboxing for months — actually face off in the ring. The debate also offers what might be a last slim hope for Martin O’Malley, Jim Webb and Lincoln Chafee to break out as a credible alternative to Sanders for primary voters who have doubts about Clinton. All three are barely registering in the polls, although CNN said they crossed the 1 percent threshold for making the stage.

Here is a look at the candidates who will field questions from that panel:

  • Clinton. Best-known in the field, she needs no introduction. She has raised the most money among the Democratic candidates and has the most endorsements. But her expected coronation has turned into a dog fight amid a lackluster campaign and questions surrounding the killing of four American diplomats in Benghazi, Libya, and her use of a private email server to conduct State Department business. Her current RealClearPolitics polling average is 42 percent.
  • Sanders. The self-styled democratic socialist served eight terms in the House of Representatives and is in his second term in the Senate. He advocates higher taxes on the rich, tuition-free college, universal child care and tough regulation of banks. He is drawing big crowds and pulled nearly even with Clinton in third-quarter fundraising. Some polls have him in the lead in the early-voting states of Iowa and New Hampshire, but his national RCP average is only 25.2 percent. The debate gives him his best shot so far to reach black voters, who overwhelmingly back Clinton.
  • Webb. A former Navy secretary in the Reagan administration, he switched parties and in 2006 won election to the Senate from Virginia. But he served only one term before retiring. Analysts once had foreseen an electoral path by appealing to working-class white men, whose economic fortunes have tumbled during the past quarter-century. But he has been invisible on the campaign trail and has failed to catch fire. RCP average is just .9 percent.
  • O’Malley. A former two-term governor of Maryland and mayor of Baltimore, his campaign strategy at the outset was simple — run to the left of Clinton and capture the hearts of the party’s progressive, activist base. But Sanders largely has usurped the role of liberal outsider, and O’Malley took a hit when his lieutenant governor lost his gubernatorial race to a Republican in a state where Democrats outnumber Republicans by a 2-1 margin. RCP average is .6 percent.
  • Chafee. The longtime Rhode Island politician has taken the most circuitous route of any of the presidential candidates. The son of a Republican scion of the state, Chafee succeeded his father in the U.S. Senate and served one full term. His liberal views were more in line with his state’s voters, but it was not enough to save him in a bad year for Republicans. He lost re-election in 2006. He later won election to the governorship as an independent and became a Democrat mid-term. But Chafee has struggled to articulate a rationale for his candidacy. When he launched his campaign in June, he said the nation should go “bold” — by adopting the metric system. RCP average stands at .2 percent.

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One prominent name will be missing: Joe Biden. CNN says it is keeping a podium for the vice president if he wants it, but he has indicated he will not join the debate, and it’s not yet clear if he is getting in the race.

CNN anchor Anderson Cooper will moderate. He will be joined on the panel by the cable network’s Dana Bash and CNN Español’s Juan Carlos López, both veteran reporters for the network. Don Lemon, who hosts his own show on CNN, will ask questions submitted by people on debate co-host Facebook.

Critics on the left are grumbling, but the panel nevertheless seems stacked with liberals.

The activist group Roots Action has complained that CNN has not included the liberal equivalent of Hugh Hewitt, a conservative radio host who was on the panel of the Republican debate last month. But while Hewitt is openly conservative, CNN’s other panelists lean left, even if they don’t always say so.

Cooper has been accused of liberal bias. Lemon barely hides his lefty opinions on the air. Bash, the network’s chief congressional correspondent, drew criticism from former Republican presidential candidate Ron Paul’s campaign after staffers claimed to have heard her expressing concerns about the candidate in a conversation with then-husband John King.

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This will also be the first debate live-streamed in a “full 3-D immersive virtual reality,” but you’ll need a Samsung GearVR headset. If you have that, you supposedly will have the perspective of someone in the audience. Not exactly like playing “Gears of War,” though.