The pressure campaign paid off, securing a 14-13 approval by the Senate Finance Committee that put Kennedy seemingly on a glidepath to confirmation as secretary of Health and Human Services in the coming days. It’s the same path taken so far by all but one of Trump’s nominees — Matt Gaetz, who withdrew his nomination for attorney general.

The last-minute maneuvering revealed a major part of the White House strategy to ensure that success: making opposition to a Trump nominee a very lonely place for a Republican.

Cassidy was not the only Republican to express reservations about Kennedy or some of Trump’s other controversial picks, including former Democratic representative Tulsi Gabbard’s nomination to be director of national intelligence. But one by one, senators released statements of support for those nominations, leaving the undecideds more and more isolated.

And Cassidy’s description of the weekend conversations with the White House and Kennedy as “very intense” might be an understatement about the pressure campaign unleashed on any Republican senator on the fence.

Vice President JD Vance, recently a senator himself, spoke with holdouts over the weekend. Pressure was also wielded by Trump ally Elon Musk, the billionaire upending the federal government while blasting any doubters with his social media megaphone and threatening primary campaigns against any senator who didn’t fall in line on nominees.

“I have received so much outreach from everybody,” Cassidy told reporters of the lobbying for his vote. “The best were, ‘Make your tough decision, and we’ll be with you.’ And the worst were — I won’t repeat what the worst were.”

Also advancing on Tuesday was Gabbard, who had convinced her skeptics on the Intelligence Committee to back her despite clearly frustrating several Republicans with her refusal to call Edward Snowden a traitor for his intelligence leaks during her confirmation hearing last week.

As with Kennedy, Maine Senator Susan Collins and a couple other GOP holdouts slowly announced their support for Gabbard, placing all the attention on Indiana Senator Todd Young. Musk posted, then deleted, a missive on X calling Young a “deep state puppet,” and subsequently praised him, saying they had a conversation and “I stand corrected.” By Tuesday morning, Young was also on board for Gabbard.

Most of the Republican senators who eventually got to yes on Trump’s nominees have cited promises from the would-be secretaries and the administration itself as making the difference.

A practicing physician for 30 years before he went into politics, Cassidy appeared to be ready to halt Kennedy’s nomination in the Senate Finance Committee, which would have deadlocked because of universal Democratic opposition.

“Regarding vaccines, Mr. Kennedy has been insistent that he just wants good science and to ensure safety,” Cassidy said on the Senate floor Tuesday, addressing his concerns. “But on this topic, the science is good. … Vaccines save lives. They are safe. They do not cause autism.”

But Cassidy said his extensive conversations with the White House and Kennedy in recent days delivered commitments that eased his mind. They included Kennedy agreeing to maintain the current Centers for Disease Control immunization recommendations, to keep statements on the CDC website that point out vaccines do not cause autism, and not to set up a parallel vaccine approval safety monitoring system.

Kennedy agreed to an “unprecedentedly close, collaborative working relationship,” Cassidy said. The two will talk or meet multiple times a month, and Cassidy will get input into HHS hires that do not have to be confirmed by the Senate.

“I will watch carefully for any effort to wrongfully sow public fear about vaccines,” said Cassidy, chair of the Senate health committee. “But my support is built on insurances that this will not have to be a concern.”

Young had a similar refrain on his support for Gabbard, saying he had a “positive conversation” with Trump, in which the president told him to “vote your conscience” and did not twist his arm.

“I said, ‘How important is this to you, Mr. President?’ And he said, ‘It’s important,’” Young told reporters after the Gabbard vote. “But he said, ‘You know what, Todd, we’re going to work together on all kinds of other things to make America great again.’ And I told him I need reassurances and those who were delivered.”

Young or Cassidy could have single-handedly derailed the nominees in committee, making it difficult for the nomination to advance to the floor.

A similar process reportedly played out with North Carolina Republican Senator Thom Tillis on the nomination of Defense Secretary Pete Hegseth. According to The Wall Street Journal, Tillis was going to provide the fateful vote against Hegseth on the floor but was told by the GOP leader that he would have to explain his vote personally to Trump, and was eventually persuaded to confirm.

Tillis told the Globe the anecdote in the Journal was “inaccurate,” and that he ultimately did not see enough corroboration of allegations by Hegseth’s former sister-in-law that Hegseth was abusive.

“It was zero,” Tillis said of the pressure. “I slept like a baby. I’d be happy to share my health monitor with you. … The administration was respectful, and there was not even a degree increase in the temperatures between me and the president.”

Senator Elizabeth Warren, who also serves on the Finance Committee, said she was skeptical of Cassidy’s decision.

“People can tell themselves whatever they need to … to vote the way they’ve decided to vote, but it doesn’t make it so,” the Massachusetts Democrat said. “The pressure on the Republicans is right in front of us. Elon Musk has said quite publicly that he will fund primary challenges to anyone who doesn’t vote the way Elon Musk thinks they should vote.”

Tillis and Cassidy are both up for reelection in 2026.

Cassidy denied that politics played into his calculus.

“I promise you, being up for reelection had absolutely zero to do with the decision,” he told reporters.

Tillis said in his remarks after the vote that he voted for Kennedy in the Finance Committee because it’s time for “a disruptor” as health secretary. Tillis also said he had concerns about Kennedy’s antivaccine views, his criticism of large agriculture companies, his calling the National Rifle Association a “terror group,” and his past support of abortion rights.

But Tillis said there was no organized opposition to Kennedy’s nomination from major outside interest groups in those areas.

“I believe that silence is consent,” he said.

Texas Republican Senator Ted Cruz, a strong Trump ally, said some of the nominees are change agents, which he understands can be disconcerting for colleagues. He acknowledged it’s one thing to vote against a nominee when there are still enough votes to confirm. It’s another to be the one to sink the nomination.

“Look, there’s no doubt that political pressure is real,” Cruz said. “One of the advantages of having a 53-vote majority is we can lose up to three senators and still prevail. I’m very glad we don’t have just a 51-vote majority.”

Kendall Wright of the Globe staff contributed to this report.

Tal Kopan can be reached at [email protected]. Follow her @talkopan. Jim Puzzanghera can be reached at [email protected]. Follow him @JimPuzzanghera.