The first round of presidential primary debates this week will give most of the two dozen Democratic contenders their biggest platform yet to present themselves to the American people.

The rapid-fire debate format — candidates will get just one minute to answer questions and 30 seconds to respond to follow-ups — may be designed for maximum fairness. But the 20 Democrats set to participate in the debates Wednesday and Thursday night are hardly coming to the Miami stage on equal footing.

For most of the candidates stuck in the low single-digits in national polls, the first debates are a chance to make a strong national introduction as much as they are a forum to lay out a policy agenda. Candidates such as Ohio Rep. Tim Ryan or New York Mayor Bill de Blasio, who cleared the threshold to take part in the debates but have yet to garner much national support, "really have nothing to lose," said Republican strategist Ford O'Connell.

It's a different story for the front-runners. Former Vice President Joe Biden, for instance, has enjoyed a consistent double-digit polling advantage since announcing his 2020 run, and he will arrive at the debate Thursday as the prime target for most of the field, political analysts told CNBC.

"He has the most to lose, and the rest of the field will have their knives out," O'Connell said. "They're coming for him, period. The only question is whether or not they're able to lay a glove on him."

Biden's campaign did not respond to CNBC's request for comment.

Biden has already weathered criticism from his competitors in the run-up to the debates. He was knocked for changing his stance on a law barring most federal funding for abortions after being slammed by Sen. Elizabeth Warren of Massachusetts. Last week, he faced a pile-on from 2020 Democrats after he cited his working relationships in the 1970s with segregationist lawmakers as an example of his ability to get things done in Congress despite personal disagreements.

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And even before Biden announced his campaign, New York Sen. Kirsten Gillibrand said the former veep would have to address allegations of inappropriate touching.

Ten candidates will debate on each of the two nights; the debates will last for two hours each and include five segments and four commercial breaks, NBC reported. The debates are being hosted by NBC News, MSNBC and Telemundo, and will air live on those networks starting at 9 p.m. ET on both nights. CNBC will also stream them.

Biden is scheduled for Thursday's debate, which includes more candidates considered to be leading the primaries than Wednesday night's roster, analysts told CNBC. California Sen. Kamala Harris, South Bend Mayor Pete Buttigieg and Vermont Sen. Bernie Sanders — all of whom have jockeyed for the top half-dozen slots in recent national polls — will stand alongside Biden on Thursday.