Jeff Zucker is a lot of things, but he is no dummy. The president of CNN saw that the second night of the first round of the Democratic presidential debates drew 18.1 million viewers, a record. Zucker employs many high-quality journalists, and he wants to contribute to the national civic dialogue. But Zucker is also very much in the ratings business, and he is in the happy position of hosting the next round. Tonight, in a live reveal, CNN will unveil the matchups, dividing the 20 candidates into two groups for the July 30 and 31 debates. The method includes an element of randomness. But Zucker is surely rooting for Kamala Harris and Joe Biden, by far the most compelling characters from the first episode of this nine-part reality series, to appear onstage together again.

Harris and Biden are less eager for a rematch, though for different reasons. Biden, the front-runner, took a series of direct hits from Harris over his Senate record of opposing busing and his recent campaign statements about chumming around with segregationists. ”It was hurtful to hear you talk about the reputations of two United States senators who built their reputations and career on the segregation of race in this country. And it was not only that, but you also worked with them to oppose busing,” Harris said, staring coldly at Biden, two podiums to her right, before dropping the sound bite of the night. “There was a little girl in California who was part of the second class to integrate her public schools, and she was bused to school every day. And that little girl was me.” Biden wanly protested that Harris had mischaracterized his position, before trying to deploy his service to Barack Obama as a shield.

The fallout has been swift. Biden’s poll numbers have dropped, and he has been forced to respond to a series of stories detailing just how lengthily and vehemently he fought the use of busing as a means to desegregate public education. CNN’s moderators are sure to question Biden about that record, no matter which night he appears, but fielding it without Harris onstage would surely dilute the discussion. “Vice President Biden is in good shape heading forward. He’s known better than any other candidate in this race. And he’s liked,” says Anita Dunn, a top Biden adviser. “His message about why he’s running—the middle-class economy, restoring the soul of America, and uniting America—is one that really does resonate with people. He will be prepared for whoever is onstage with him. And he will continue to live by his rule, which is, he views the Democratic field as competitors and his opponent as Donald Trump. But I think it is unlikely he will allow any candidate to distort his record the way that his record was distorted in the first debate—particularly someone who ended up agreeing with his position.”

Ed Rendell, a former Pennsylvania governor who is backing Biden, suggests some specific tactics. “He doesn’t need to refute Harris on busing. But he does need to be proud of what he’s done, and be aggressive,” Rendell says. “So if someone comes after him on, say, the crime bill, he should say, ‘I want to be judged on the totality of my 45-year career in public service.’ Then lean over to Kamala Harris and say, ‘I guess you wouldn’t want someone to look at all the cases you prosecuted as D.A. of San Francisco and attorney general of California and find somewhere you made a mistake. You’d want them to bring up your total record, right?’”