Dr. Anthony Fauci, the U.S. scientist who helped lead the nation’s COVID-19 pandemic response, is set to face off — again — with a Republican senator probing the origins of the coronavirus.

Sen. Rand Paul of Kentucky subpoenaed Fauci to appear before a Senate committee Wednesday. It’s part of Paul’s yearslong accusations that the now-retired infectious disease expert had lied about the pandemic, something Fauci has called “preposterous.”

Leading up to the hearing, Paul released more than a thousand pages of Fauci’s personal diary covering the pandemic years. Pointing to some notes about early efforts at understanding how the virus emerged, Paul wrote on the social media platform X that what Fauci “wrote privately and what he told the country are two different stories.”

Some of the diary entries — including his uncertainty in the pandemic’s earliest days as scientists around the world raced to understand the new virus and how best to curb it before vaccines could be created — already were reflected in Fauci’s 2024 memoir and in interviews at the time.

But they’re likely to further inflame a partisan divide that, years after the pandemic, still makes Fauci a target of vitriol from people who blame him for mask mandates and other policies they believe infringed on their rights as hundreds of thousands of people were dying.