“Everyone wants to describe the day that the light switch flipped and the C.D.C. was sidelined. It didn’t happen that way,” Mr. McGowan said. “It was more of like a hand grasping something, and it slowly closes, closes, closes, closes until you realize that, middle of the summer, it has a complete grasp on everything at the C.D.C.”

Last week, the editor in chief of the C.D.C.’s flagship weekly disease outbreak reports — once considered untouchable — told House Democrats investigating political interference in the agency’s work that she was ordered to destroy an email showing Trump appointees attempting to meddle with their publication…

Mr. McGowan and Ms. Campbell, both 34, say they tried to protect their colleagues against political meddling from the White House and Department of Health and Human Services. But an agency created to protect the nation against a public health catastrophe like the coronavirus was largely stifled by the Trump administration.

The White House insisted on reviewing — and often softening — the C.D.C.’s closely guarded coronavirus guidance documents, the most prominent public expression of its latest research and scientific consensus on the spread of the virus. The documents were vetted not only by the White House’s coronavirus task force but by what felt to the agency’s employees like an endless loop of political appointees across Washington.