That is not quite how Medicaid works, Mr. Kennedy. Robert F. Kennedy Jr. said Wednesday “most Americans are not happy” with Medicaid because “the premiums are too high,” suggesting he may be oblivious to the fact that Medicaid overwhelmingly does not have premiums.

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.