Klobuchar vs. Buttigieg: Senator Amy Klobuchar of Minnesota has made little secret of her displeasure that lesser-experienced male candidates like Mayor Pete Buttigieg of South Bend, Ind., and Beto O’Rourke, the former Texas congressman, received gobs of media attention that has yet to come her way. Now she will be standing next to Mr. Buttigieg, and have her chance to take him down a peg.

Booker vs. Biden: Before Ms. Harris went after Mr. Biden during the first debate, it was Mr. Booker who demanded he apologize for praising segregationist senators. But unlike Ms. Harris, Mr. Booker didn’t sustain the attack. Now he will have a chance, as he stands next to the former vice president.

Inslee vs. the moderators: Gov. Jay Inslee of Washington has made his campaign a crusade to discuss climate change, a topic that received little airtime in the first set of debates. Expect a lot of griping from him about the topic getting short shrift, no matter how much it is discussed in Detroit.

[Want a preview of the next debates? Nearly all the Democratic hopefuls were in Detroit on Wednesday.]

How did they draw the names?

CNN divided the field into two groups of 10 candidates as only the network could. There were dark blue cards and light blue cards, and three tiers of candidates, each with their own box to be drawn from. (The campaigns were allowed to inspect the boxes before the drawing, a person involved in the inspection said.)

In what could have passed for a parody of an N.F.L. pregame show, the network showed three simultaneous camera shots of the live drawing, so viewers at home could see the inside of the box as well as the CNN personality as they lifted the cards out.

And there was plenty of commentary about who might wind up on which night before the cards were drawn — a delay to add tension to what was, literally, picking names out of a box.