Sen. John Fetterman (D., Pa.), who had said he was open to hearing out Robert F. Kennedy Jr., expressed more doubts about the Health and Human Services nominee after his first confirmation hearing Wednesday before the Senate Finance Committee.

Sen. John Fetterman (D-Pa.), who was thought to be open to voting for Robert F. Kennedy Jr.’s nomination to head the Department of Health and Human Services, now says the nominee is in serious

Kennedy Jr. rejected characterizations of him as an anti-vaxxer in a Senate hearing Wednesday where senators will weigh his confirmation as Health and Human Services Secretary—as his former billionaire running mate threatens to fund primary challenges against lawmakers who vote against him.

Robert F. Kennedy Jr. said he wasn’t antivaccine as senators pressed on his past remarks, in the first of two days of hearings over his nomination for health secretary.

Some GOP senators want public commitments from Robert F. Kennedy Jr. before deciding whether to support him as the next secretary of the Department of Health and Human Services, signaling that President Donald Trump’s pick will have to win over uncertain Republicans in order to secure the job.

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.

The hearings were packed to capacity with protesters and fans, while the spillover crowd hung out in hallways and overflow rooms.

Robert F. Kennedy, President Trump’s nominee for health secretary, vigorously defended his views on vaccines, and a key senator still has clear doubts.

Democrats focused on Kennedy's anti-vaccine advocacy. Republicans probed the former Democratic leader on his abortion and agriculture views.