Dr. Anthony S. Fauci after President Trump referred to the “Deep State Department” at a briefing on March 20.
Credit: Erin Schaff/The New York Times

At a White House briefing on the coronavirus on March 20, President Trump called the State Department the “Deep State Department.” Behind him, Dr. Anthony S. Fauci, the director of the National Institute of Allergy and Infectious Diseases, dropped his head and rubbed his forehead.

Some thought Dr. Fauci was slighting the president, leading to a vitriolic online reaction. On Twitter and Facebook, a post that falsely claimed he was part of a secret cabal who opposed Mr. Trump was soon shared thousands of times, reaching roughly 1.5 million people.

A week later, Dr. Fauci — the administration’s most outspoken advocate of emergency measures to fight the coronavirus outbreak — has become the target of an online conspiracy theory that he is mobilizing to undermine the president.

That fanciful claim has spread across social media, fanned by […]