Robert F. Kennedy Jr.'s record of questioning childhood vaccine safety came under fire from a key Republican at the Trump HHS pick's confirmation hearing.

The questioning comes after Robert F. Kennedy Jr. faced grueling testimony on Thursday to secure the Secretary of Health and Human Services position

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.

The health committee chairman, Sen. Bill Cassidy, R-La., also has expressed concerns about Kennedy's anti-vaccine work. A physician, Cassidy said earlier this month he “had a frank conversation” and “spoke about vaccines at length” with Kennedy. On Tuesday, Cassidy told reporters that he is still unsure if he is backing Trump’s nominee.

Senator Bill Cassidy, a physician and key G.O.P. vote, joined Democrats in aggressively questioning Robert F. Kennedy Jr., President Trump’s pick for health secretary. He did not say how he would vote.

Robert F. Kennedy Jr. is seeking the support of the Republican-controlled Senate in his bid to become the nation’s top health official.

Caroline Kennedy, daughter of former President John F. Kennedy, warned senators of her “predator” cousin ahead of his first confirmation hearing on Wednesday. In a letter first reported by The Washington Post, she wrote that his victims included family members and parents of sick children.

Mr. Kennedy appears to have most Republicans behind him as he seeks the job of health secretary, though he couldn’t escape his past stances on vaccines and abortion.

Robert F. Kennedy Jr. has said vaccines are not safe. His support for abortion access has made conservatives uncomfortable. And farmers across the Midwest are nervous over his talk of banning corn syrup and pesticides from America’s food supply.

To watch Kennedy's confirmation hearing, viewers can look to the Senate Finance Committee website on Wednesday and the Senate Health, Education, Labor and Pension Committee website on Thursday. C-SPAN and a plethora of broadcast and cable media outlets will broadcast live what is likely to be a contentious confirmation hearing on television.

Alaska U.S. Sen. Lisa Murkowski called the nominee an “influencer” and spoke about the importance of vaccines in Alaska.