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Candidates will have 60 seconds to answer questions and 30 seconds to respond to follow-ups. And there will be no opening statements, though candidates will have a chance to deliver closing remarks.
The two-hour debates will zip by quickly, with five segments each night separated by four commercial breaks.
Ten candidates will face off each night on NBC News, MSNBC and Telemundo after a total of 20 candidates met the Democratic National Committee's threshold for participation.
With so many candidates, there's only so much time to go around.
"It's a little bit of exaggeration calling it a debate," former Vice President Joe Biden joked in Iowa earlier this month. "It's like a lightning round."
Candidates have been preparing for the tight squeeze by having aides time their responses to questions as they work to tighten and hone answers.
For many lesser-known candidates, the debates will their first chance to introduce themselves to a larger national audience, so they know they have to try to pack a lot into a small amount of time.
Download the NBC News app for full coverage of the first Democratic debate
And for some better-known candidates, it might mean having to defend controversial policies or parts of their records quickly in order to give them enough time to try to finish with something positive.
Savannah Guthrie, Lester Holt, Chuck Todd, Rachel Maddow and José Diaz-Balart will moderate the debates from the Adrienne Arsht Center in Miami.