Dr. Anthony Fauci and President Donald Trump went from close collaborators during the early days of the COVID-19 pandemic response to political adversaries in one of the most consequential and public breakdowns of Trump’s first term.

At the outset, Trump regularly praised Fauci, the nation’s top infectious disease expert, calling him “a terrific guy” and “a wonderful man.” Fauci became a fixture at White House Coronavirus Task Force briefings, often standing beside the president as the administration sought to project a united front.