The format
The debate will begin with one-minute opening statements, followed by questions from the moderators: George Stephanopoulos, David Muir and Linsey Davis from ABC and Jorge Ramos from Univision.
ABC told the campaigns there would be just two commercial breaks, one after about 45 minutes of debating and the other after about 90 minutes. The candidates will debate for another 30 minutes after the second commercial break.
The breaks will be lengthy — four minutes each, according to ABC. There will be no closing statements.
The dynamics
With Mr. Biden and Ms. Warren onstage together for the first time, the moderators are certain to try to bait them into confronting each other. The pair have a long history, stretching back to a battle in a 2005 Senate hearing over a credit card industry-supported bankruptcy bill Mr. Biden backed and Ms. Warren, then a Harvard law professor, opposed.
Expect other fireworks along the way.
Ms. Harris has seen her campaign flag after her debate-stage confrontation with Mr. Biden over busing and school segregation gave her a lift, and so has Mr. Buttigieg, who since Labor Day has signaled that he’s prepared to be more combative with the race’s front-runners.
Mr. Sanders is likely to take his grievances straight to the moderators, a tactic that could draw in Ms. Klobuchar as well.
And then there is Mr. O’Rourke, appearing on a debate stage for the first time since the mass shooting in his hometown, El Paso, transformed his campaign from one focused on Iowa to one hopscotching the country addressing various injustices past and present.
He’s also come out with the most robust gun control proposal in the field, arguing for a buyback program that would require owners of assault-style firearms to sell them to the federal government. Mr. O’Rourke hasn’t focused on drawing contrasts with fellow Democrats so far, but he has a chance to try to shame his rivals on gun safety Thursday night.
His repeated swearing on the campaign trail prompted ABC to send a memo to the campaigns Tuesday warning that the debate would be broadcast without a delay and “candidates should therefore avoid cursing or expletives in accordance with federal law.”
The wild card is Mr. Yang. He’s far exceeded expectations and could serve purposes ranging from comic relief to outsider breath of fresh air.
Mr. Yang’s campaign seems to understand this as his place in the debate. A spokesman promised Wednesday that Mr. Yang would make an announcement that would “break the mold of presidential politics” at the debate, but did not elaborate.
The stakes
Little that happened in the first two debates changed the long-term nature of the 2020 campaign. The viral moments that did happen became political cotton candy — a sugar high that quickly dissipated and left the candidates involved with more of a stomachache than a permanent advantage.
For the leading candidates, that means their primary responsibility is to survive and advance to the subsequent rounds of debates. This is all but assured for Mr. Biden, Ms. Warren, Mr. Sanders, Ms. Harris and Mr. Buttigieg.
But the others may need a boost to remain on the debate stages come November and December, after the Democratic National Committee raises the donor and fund-raising thresholds required to qualify. Mr. O’Rourke and Ms. Klobuchar have sent fund-raising appeals stressing this point; Mr. Booker’s campaign aides have had internal deliberations on what they may need to change to keep their candidate on the debate stage.
Matt Stevens contributed reporting.