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.

Sen. Bill Cassidy, the top Republican on the Senate Committee on Health, Education, Labor and Pensions, concluded Thursday's hearing by saying he was "struggling" with the nomination due to Kennedy's vaccine positions. Kennedy notably refused to say vaccines don't cause autism as he faced pointed question from lawmakers.

Caroline Kennedy on Tuesday warned that her cousin Robert F. Kennedy Jr. is a “predator” ahead of his high-profile confirmation hearings this week to be President Donald Trump’s Department of Health and Human Services secretary,