Robert F. Kennedy Jr. faced aggressive questions about his skepticism of vaccines and other issues during the first of two scheduled Senate confirmation hearings.

WASHINGTON — Robert F. Kennedy Jr.’s anti-vaccine advocacy is outside the mainstream. His previous statements on abortion could alienate Republicans. But a new poll finds that not all of his controversial health goals are unpopular — in fact, at least one has broad support among Democrats and Republicans.

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.