RFK Jr. Faced Congress. A Physician-Senator’s Competing Loyalties Were on Display.

A Republican senator juggling three roles — lawmaker, doctor, and political candidate seeking reelection — walked a fine line on Wednesday as he questioned Health Secretary Robert F. Kennedy Jr., a longtime anti-vaccine activist who has moved to dramatically roll back the nation’s childhood vaccine recommendations.

Louisiana Sen. Bill Cassidy, MD, who chairs one committee that oversees Kennedy’s department and sits on another, took a tough but measured posture in two high-stakes hearings Wednesday, where he asked the health secretary about affordability, fraud, abortion drugs, and the rise of vaccine-preventable diseases like measles.

A liver doctor, Cassidy has clashed with Kennedy’s vaccine agenda even though he provided crucial support for the health secretary’s nomination last year.

At the same time, Cassidy is fighting for his political future in next month’s primary in Louisiana, where President Donald Trump has endorsed one of his opponents in an unusual attempt to oust a sitting senator from his own party.

Ahead of Wednesday’s hearings, experts said his handling of them could affect his chances at a pivotal moment of his reelection campaign and set the tone for how Congress oversees the nation’s health agenda at a time of rampant distrust and misinformation.

“He’s taken a risk showing any sort of resistance to RFK,” said Claire Leavitt, PhD, an assistant professor at Smith College who studies congressional oversight. “He may pay an electoral price for that.”

Cassidy took that chance on Wednesday, noting that trust in vaccines has declined in the U.S. over the past year and asking Kennedy how he would address expected outbreaks of vaccine-preventable diseases with the upcoming World Cup and America 250 events.

“I am a doctor who has seen people die from vaccine-preventable diseases,” Cassidy said. “And when I see outbreaks numbering in the thousands and people dying once more from vaccine-preventable diseases, particularly children, it seems more than tragic.”

Louisiana political consultant Mary-Patricia Wray said the senator’s approach was like a “polite ‘I told you so.'”

“Cassidy reinforced the real-world consequences of declining vaccine confidence while subtly signaling that the administration’s posture is moving closer to where he has been as a physician,” Wray said.

Cassidy Has Long Advocated for Vaccines

Cassidy has spent years walking a political tightrope. He’s one of the few Republican senators who voted to convict Trump during an impeachment trial after the Jan. 6, 2021, attack on the U.S. Capitol.

As a liver doctor, he advocated for babies to receive hepatitis B vaccines shortly after birth, a step that could have prevented the disease in his patients. But when Trump nominated Kennedy, a longtime anti-vaccine activist, Cassidy supported him. He did so after securing various commitments, including that Kennedy would work within the current vaccine approval and safety monitoring system and support the childhood vaccine schedule.

The vote for Kennedy did not appear to mollify Trump. The president endorsed U.S. Rep. Julia Letlow, one of Cassidy’s two primary opponents.

Cassidy also faces opposition from Kennedy’s allies in the “Make America Healthy Again (MAHA)” movement, a group that includes both anti-vaccine activists and a wide variety of other crusaders for health and the environment. The MAHA PAC, aligned with Kennedy, has pledged $1 million to Letlow’s campaign. While the organization hasn’t publicly said so, some have questioned whether the support is partly in retaliation against Cassidy for criticizing Kennedy’s vaccine policy agenda.

“I’m not really sure what MAHA’s beef is,” Cassidy told reporters earlier this month. “Let me point out that I am the reason that Robert F. Kennedy is now the secretary of HHS. He would not have gotten there otherwise.”

Cassidy argues that he has “strongly supported” the MAHA agenda, especially when it comes to the fight against ultraprocessed foods. However, the physician-turned-senator acknowledged that he and MAHA have “disagreed on vaccines.”

“We’ve seen, frankly, that I am right,” Cassidy added, pointing to recent measles-related deaths of children who were not vaccinated.

At a hearing in September, he slammed Kennedy’s decision to slash funding for mRNA vaccine development. He interrogated Kennedy over his attempt to replace members of a vaccine committee, suggesting the new members could have conflicts of interest. He also raised concerns that Kennedy’s vaccine policy decisions could be making it harder for Americans to get COVID-19 shots.

Later that month, Cassidy convened a hearing featuring former CDC Director Susan Monarez, PhD, who was ousted by Kennedy less than a month into her tenure after they clashed over vaccine policy, and former CDC Chief Medical Officer Debra Houry, MD, MPH, who resigned in August citing an erosion of science at the agency.

“I want to work with the president to fulfill his campaign promise to reform the CDC and Make America Healthy Again. The president says radical transparency is the way to do that,” Cassidy said at the time.

Experts Say Cassidy’s Vaccine Stance Might Not Hurt Him

Political consultants said they expect Cassidy’s primary opponents, Letlow and Louisiana Treasurer John Fleming, MD, to seize on any sound bites from Wednesday’s hearings that can make Cassidy seem at odds with the Trump administration.

But Dorit Reiss, a vaccine law expert at UC Law San Francisco, said the political risk of his vaccine advocacy may not be as strong among Republicans as some people assume. That’s in part because Kennedy and the Trump administration have recently pivoted away from discussing vaccines, focusing instead on less controversial topics like healthy eating.

“He’s probably not alienating voters by focusing on the issue and calling it out,” she said.

Cassidy also showed during Wednesday’s hearings a willingness to be tough on Kennedy from the political right. He asked Kennedy why HHS hasn’t reinstated an in-person dispensing requirement for chemical abortion drugs.

Through that line of questioning, Wray said, he’s courting non-MAHA Republican voters who want to see the Trump administration do more on their priorities.

He’s proving that “working with this administration doesn’t mean he works for this administration,” Wray said.

Election Outcome Will Shape Future Oversight of HHS

Also at stake if Cassidy doesn’t make it to November’s general election is what will happen to his responsibility to oversee the massive Department of Health and Human Services as the chair of the Senate Health, Education, Labor, and Pensions committee.

Leavitt, the Smith College professor, said seniority typically plays the most important role in who chairs Senate committees. She said another Republican in today’s increasingly hyperpartisan Congress may not be as willing as Cassidy to check Kennedy’s power.

Reiss, the vaccine law expert, said she wishes Cassidy had done more hearings or introduced legislation to rein in Kennedy. And she said the senator bears the blame for allowing Kennedy to bring unfounded vaccine fears into the government in the first place.

“His original sin, of course, was voting for Kennedy at all,” Reiss said.