The format

The debates will begin with 60-second opening statements, followed by 60-second responses to questions posed by CNN’s moderators, Dana Bash, Don Lemon and Jake Tapper.

CNN will not ask the candidates “show of hands” questions. And representatives from the network have told the campaigns they will penalize any candidate who “consistently interrupts” by reducing the amount of time that candidate has to speak.

The candidates will appear at the Fox Theater in downtown Detroit, a venue that hosted the infamous 2016 Republican presidential primary debate in which Donald J. Trump defended the size of his manhood after Senator Marco Rubio of Florida attacked it.

The dynamics

On the first night, CNN’s moderators will undoubtedly seek to draw distinctions between Mr. Sanders and Ms. Warren. Others onstage will also seek to contrast themselves with the race’s leading progressives. Senator Amy Klobuchar of Minnesota has, in recent interviews, foreshadowed a resistance to the free college and Medicare for All proposals pushed by Mr. Sanders. Former Gov. John Hickenlooper of Colorado and former Representative John Delaney of Maryland oppose socialism and have attacked Mr. Sanders, a democratic socialist, without much success. Gov. Steve Bullock of Montana, who did not qualify for the first debate in June, has said since then that he would not support extending federal health care benefits to undocumented immigrants, separating himself from most of the presidential field.

More prospective sources of tension might include a battle between Mayor Pete Buttigieg of South Bend, Ind., and former Representative Beto O’Rourke of Texas — a conflict Mr. O’Rourke’s allies have foreshadowed in recent days. Ms. Klobuchar, meanwhile, has barely hid her disdain for Mr. Buttigieg and Mr. O’Rourke, two men who are younger and less accomplished than her but have received far more attention in the race. And Marianne Williamson, a self-help author, remains a wild card.

While all 10 candidates debating on Tuesday are white, Wednesday’s debate will feature five people of color, including Ms. Harris and Mr. Booker, who have each placed their bets on wresting the support of black voters away from Mr. Biden.

There’s little doubt Mr. Biden’s record on race will be a focus. Ms. Harris’s broadside during the first debate against Mr. Biden’s decades-old position on mandatory busing to integrate public schools energized her campaign, while Mr. Booker last week hit Mr. Biden for writing the 1994 crime bill, previewing a line of attack.