Mr. Feist said that cleaners were wiping down doorknobs and other hard surfaces in the bureau “multiple times an hour,” with extra attention to areas that “a guest, a CNN staffer, or, in this case, a candidate might enter or touch.”
Sunday’s broadcast is thought to be the first presidential debate to be held in a closed television studio since the Kennedy-Nixon debates of 1960, according to Mr. Feist. Those encounters, the first televised debates of the mass media age, took place at television stations in Chicago, Los Angeles, New York and Washington.
With only Mr. Biden and Mr. Sanders onstage, it will also be the smallest Democratic debate of the campaign; several earlier debates featured as many as 20 candidates and had to be spread over two nights. Timing rules will be similar to past debates, with 75 seconds allotted for each candidate’s response, though fewer zingers and zippy sound-bites are expected.
“Debates with two candidates tend to be more of a conversation than other debates because time is less of a factor,” Mr. Feist said. “While those are the rules, the reality of a debate with two candidates is that it’s likely to be more conversational.”
Sunday’s debate was originally planned for an Arizona theater with a large audience. CNN, Democratic officials and the campaigns agreed to move the location to Washington, reducing the need for hundreds of political aides, journalists and TV crew members to take cross-country flights.
The CNN anchors Dana Bash and Jake Tapper, along with the Univision anchor Ilia Calderón, will serve as moderators. Another moderator, Jorge Ramos of Univision, relinquished his spot as a precaution after he believed he had been possibly exposed to the coronavirus; Mr. Ramos has no symptoms and has said he feels healthy.
The absence of a live audience will add an additional wrinkle for two candidates accustomed to the reactions of a crowd. Mr. Biden and Mr. Sanders will also be standing at their lecterns when the broadcast begins, Mr. Feist said, so viewers will not see a dramatic entrance.