Mr. Trump called Dr. Francis S. Collins, the N.I.H. director, after he and other senior government scientists had stepped in to slow an emergency approval to expand the use of blood plasma from recovered Covid-19 patients to treat new ones. For more than a week, the N.I.H. had held up the emergency authorization, citing concerns over the effectiveness of so-called convalescent plasma.
With White House officials anxious to showcase a step forward in the battle against the virus, Mr. Trump was having none of it: “Get it done by Friday,” he demanded.
That Sunday night, the eve of the Republican National Convention, the president had what he wanted: He announced that plasma therapy had been approved for wider use, and he declared that it could reduce deaths by 35 percent, vastly overstating what the data had shown about the benefits.
Mr. Trump’s call to Dr. Collins was just one in a series of moments that have left scientists and regulators across the public health bureaucracy increasingly worried that the White House could exert even greater pressure to approve a vaccine before Election Day, even in the absence of agreement on its effectiveness and safety.
On the night of the plasma announcement, Dr. Collins was told to show up at the White House, where he was given a coronavirus test and then shunted to the Roosevelt Room as Mr. Trump and others spoke to journalists in the briefing room.
There, Dr. Collins and Dr. Peter Marks, one of the top regulators at the Food and Drug Administration and the person most directly responsible for maintaining the independence and scientific rigor of the vaccine approval process, watched helplessly as the president and other top administration officials oversold plasma’s effectiveness, creating a public relations debacle that reverberated for days.
Dr. Collins left the White House after the announcement. But Dr. Marks, who had pushed for the plasma approval, was escorted to the Oval Office to spend a few minutes with Mr. Trump and his top aides, who were celebrating with cupcakes with white icing. In an interview on Friday, Dr. Marks said he was “a little bit in a state of shock” to find himself there.