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

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.

Senators grilled Robert F. Kennedy Jr. on if and how he would reform Medicaid and Medicare during his first confirmation hearing to become the next secretary of Health and Human Services.