Kennedy struggled to identify and explain the fundamental aspects of Medicare, which provides coverage to older and disabled Americans.

If approved, Kennedy will control a $1.7 trillion agency that oversees food and hospital inspections, hundreds of health clinics, vaccine recommendations and health insurance for roughly half the country.

Robert F. Kennedy Jr., nominee for HHS secretary, seemed unfamiliar with the massive insurance program during Thursday’s hearing, mistakenly saying Medicare Part A mainly paid for primary care or physicians.