Following a testy confirmation hearing on Wednesday, it is clear that the nominee to lead the Department of Health and Human Services, Robert F. Kennedy Jr., is far from a shoe-in for the position, as senators asked questions about his vaccine skepticism, his record on abortion rights, and his potential conflicts of interest. Support from powerful outside forces could buoy his chances, however. 

Mr. Kennedy’s confirmation hearing for the Senate Finance Committee on Wednesday saw Democrats press the nominee on his record and his plans just months after he dropped his independent presidential bid and offered his support to President Trump. On Thursday, when he sits before the Health, Education, Labor, and Pensions Committee, things likely will not be much better. The chairman of the HELP Committee, Senator Cassidy, has so far not yet offered his support to the nominee. 

The Kennedy scion’s outside friends are already stepping up their pressure campaign to threaten those lawmakers who refuse to support him. His running mate during his independent run for the White House, Nicole Shanahan, said she would exact revenge on those who didn’t back Mr. Kennedy. She made it clear her threat was bipartisan, and that she would use her vast personal fortune to spend on Senate elections. 

“In 2020, I cut large checks to Chuck Schumer to help Democrats flip two Senate seats in Georgia from red to blue. The two candidates I helped elect — Senator Raphael Warnock and Senator Jon Ossoff — please know that I will be watching your votes very closely,” she said in a video posted to X. “I will make it my personal mission that you lose your seats in the Senate if you vote against the future health of America’s children.”

Ms. Shanahan further listed Senator McConnell, Senator Murkowski, Senator Collins, Senator Graham, Senator Booker, Senator Fetterman, Senator Tillis, Senator Lankford, Senator Sanders, Senator Cortez Masto, and Mr. Cassidy as other lawmakers who need to get on board with Mr. Kennedy’s nomination. 

“While Bobby may be willing to play nice, I won’t,” she warned. 

The head of the conservative group Turning Point USA, Charlie Kirk, issued a similar threat to lawmakers. “Confirm Bobby Kennedy or face well funded primary challenges. Choose wisely,” he wrote on X.

On Wednesday, Democrats and Republicans alike pressed Mr. Kennedy on his pro-abortion rights stance. He has promised the GOP that he would enforce Mr. Trump’s policies to help scale back the number of abortions in America, though Democrats were quick to point out that he was a fiercely pro-abortion rights presidential candidate just a few months ago. At his first hearing, Mr. Kennedy said he has been directed by Mr. Trump to “study” the safety of the medical abortion pill mifepristone. 

“We need to understand the safety of every drug — mifepristone and every other drug,” Mr. Kennedy said. As health and human services secretary, he could play a critical role in that fight if Mr. Trump asks him to use his authority to declare the pill unsafe by the Food and Drug Administration’s standards. 

“President Trump has made it clear to me that one of the things he is not taking a position yet on is mifepristone. … He’s made it clear to me that he wants to take a look at safety issues, and I’ll ask NIH and FDA to do that,” Mr. Kennedy said. 

Democrats lambasted Mr. Kennedy for his compliance with Mr. Trump’s abortion rights views, including the banning of public funds for abortion under Title X. 

“You clearly stated in the past that bodily autonomy is one of your core values,” Senator Hassan told the nominee on Wednesday. “The question is: Do you stand for that core value or not? When was it that you decided to sell out the values you’ve had your whole life in order to be given power by President Trump?”

“I think everybody on that side is pro-life,” Senator Sanders said, gesturing to his Republican colleagues on the committee, before pointing to his fellow Democratic caucus members to say, “everybody here is pro-choice.”

“I have never seen any major politician flip on that issue quite as quickly as you did when Trump asked you to become HHS secretary,” the Vermont lawmaker exclaimed. 

Sitting behind Mr. Kennedy through his hours-long hearing on Wednesday was his wife, actress Cheryl Hines, other family members, and conservative media personality Megyn Kelly. Further back, Mr. Kennedy had a throng of supporters who would applaud loudly whenever the nominee got into it with a member of the Senate Finance Committee. 

One of the most heated moments of the day was when Senator Warren asked Mr. Kennedy if he would divest from an ongoing lawsuit against the pharmaceutical company Merck, which is a substantial source of income for Mr. Kennedy and his wife. Wisner Baum — a law firm where Mr. Kennedy serves as a consultant — is in the middle of suing Merck for not providing information about the risks of their HPV vaccine, and Mr. Kennedy is entitled to ten percent of all payouts for those claimants. According to his financial disclosure, Mr. Kennedy made more than $850,000 from his Wisner Baum consultancy in the last year. 

Ms. Warren asked Mr. Kennedy if he would stop taking the ten percent payout while he is serving as secretary, given he would oversee the agencies that regulate Merck. The nominee said he would not divest from his stake. 

“You’re asking me not to sue drug companies,” Mr. Kennedy said, leading Ms. Warren to interrupt with a “No!”

“I’m not gonna agree to that, senator,” Mr. Kennedy said, pointing his finger at her, leading his supporters in the crowd to applaud.