The first time I talked to Dr. Fauci was during a panic in the mid-80s about stopping another virus, the cause of the heartbreaking AIDs crisis. Then, as now, he was honest, brave and innovative. He told me that he tries to be diplomatic when he has to contradict the president about what “game-changer” cures might be on the horizon and whether everyone who wants to be tested can get tested.

“I don’t want to embarrass him,” the immunologist says, in his gravelly Brooklyn accent. “I don’t want to act like a tough guy, like I stood up to the president. I just want to get the facts out. And instead of saying, ‘You’re wrong,’ all you need to do is continually talk about what the data are and what the evidence is.

“And he gets that. He’s a smart guy. He’s not a dummy. So he doesn’t take it — certainly up to now — he doesn’t take it in a way that I’m confronting him in any way. He takes it in a good way.”

On Friday, a trigger-happy Trump was so quick to talk up the fabulous possibilities of an antimalarial drug in combating the virus that Dr. Fauci had to pump the brakes, taking the microphone to explain that we do not know yet because controlled testing is needed.

The president returned to the lectern to press his unscientific case and compliment himself: “I’m a smart guy,” he said. “I feel good about it. And we’re going to see. You’re going to see soon enough.”

Probably thinking about all his government staffers working round-the-clock, Dr. Fauci could not help rubbing his forehead and cheek — going against his own advice to the public — when Trump cracked a joke about the “Deep State Department.”

Though the scientist listens respectfully when the president and the vice president are talking, he somehow manages to emit an “Oh my God, please don’t say that” vibe when the two men scamper over the line. When Mike Pence went into false-hope overdrive, saying, “I just can’t emphasize enough about the incredible progress that we have made on testing,” Dr. Fauci and Dr. Deborah Birx, the administration’s virus response coordinator, exchanged a whispered aside that sent the internet into a frenzy.