Debate Will Be 90 Fateful Minutes for 2 Candidates, and One Network

Tens of millions of Americans will tune in live on Tuesday to see how Vice President Kamala Harris and former President Donald J. Trump handle their first head-to-head encounter on the debate stage.

That mass audience will also scrutinize the performance of ABC News.

As the sponsor and host of a general-election debate, ABC is in charge of nearly every aspect of the presentation, from the camera angles that viewers see at home to the ability of the moderators, David Muir and Linsey Davis, to keep the proceedings on track.

TV networks prefer to recede into the background on a debate night. But ABC has already found itself at the center of crisscrossing accusations from both campaigns. Ms. Harris’s aides have complained that some ground rules disadvantage the vice president. Mr. Trump, meanwhile, has assailed the network in increasingly belligerent ways, deeming ABC “the worst” and “the nastiest.”

Leaders at ABC News, who were gathering at the debate site in Philadelphia on Saturday, say they have shrugged off the noise, noting that both campaigns ultimately agreed to participate.

“I don’t think anything that is said about us or about the debate changes our role or our mission,” Rick Klein, the network’s political director, said in an interview. “Our job is to meet the moment, and it’s a huge moment and a humbling moment. Nothing that’s said about us or anyone else matters once the light goes on and the cameras are rolling.”

Still, the network, which recently endured a tumultuous leadership change, is aware that Tuesday night is a moment of both opportunity and peril.