Dr. Anthony Fauci, the U.S. scientist who helped lead the nation's COVID-19 pandemic response, is facing off with a Republican senator probing the origins of the coronavirus. Sen. Rand Paul of Kentucky subpoenaed Fauci to appear Wednesday before a Senate committee, part of Paul's yearslong accusations that the now-retired infectious disease expert had lied about the pandemic. Fauci has called that “preposterous” in prior hearings and his lawyers likewise call the allegations “absolutely baseless.” Many scientists believe the coronavirus likely jumped from animals to people in nature. Paul champions a theory that it may have leaked from a laboratory.