Robert F. Kennedy's nomination will put Republican lawmakers' loyalty to the test, as the former Democrat holds a range of unorthodox positions that could alienate both conservatives and liberals.

The former Democrat, nominated by US president Donald Trump to be his health secretary, had a hard time justifying anti-vax statements he previously made.

If confirmed by the Senate, Kennedy would head the Department of Health and Human Services (HHS), which oversees many of the country’s health agencies, from the Food and Drug Administration (FDA) to the Centers for Disease Control and Prevention (CDC).