Here are two examples of the split. A group aligned with former Vice President Mike Pence launched a six-figure ad buy on Fox News to try to sink Kennedy’s nomination, while philanthropist Nicole Shanahan, Kennedy’s former running mate, has vowed to “personally fund” primary challenges against senators who oppose him. “While Bobby may be willing to play nice, I won’t if you vote against him,” she said in a video posted to X last week.

Shanahan, like Kennedy, is a newcomer to the GOP electoral coalition. Both have a history of progressive politics. Kennedy is a literal son of the first family of American liberalism. Pence was President Donald Trump’s vice president during his first term. Also a former Indiana governor and Republican Study Committee chairman, he has deep roots in the conservative movement and is railing against Kennedy’s past advocacy of unrestricted abortion and government-run healthcare, in addition to his vaccine skepticism. Pence’s ad uses Trump’s own words against Kennedy.

But Kennedy and Shanahan ended their campaign as an independent presidential ticket and endorsed Trump last year. Pence split with Trump over Jan. 6 and the 2020 election results and did not back the president in 2024.

Trump was able to win 82% of evangelicals, according to exit polls, without Pence’s support. He also carried Catholics by 20 points and won huge majorities among voters who believe abortion should be illegal in all or most cases, despite failing to endorse a federal abortion ban. Religious conservatives are Pence’s base and he was chosen as Trump’s running mate in 2016 to help build bridges to evangelicals.

Trump also won the national popular vote in addition to the Electoral College this time around with at least some help from crossover voters who liked Kennedy. Exactly how much is unclear. Kennedy remained on the ballot in some states and received 756,393, or less than 0.5% of the total, for a distant fourth-place showing behind the Green Party’s Jill Stein. But he at one point polled as high as 16% nationally in a CNN-SSRS poll and was polling within the margin between Trump and former Vice President Kamala Harris both nationally and in several battleground states when he dropped out.

Kennedy began to hemorrhage left-wing support in some polls after Harris replaced former President Joe Biden, whom Kennedy originally intended to run against in the Democratic primaries, at the top of the ticket. Some believe his remaining anti-establishment and disaffected conservative voters gave Trump a boost. (Trump’s anti-Kennedy comments that Pence quotes were made when Mar-a-Lago viewed Kennedy as an electoral threat.) The president rewarded Kennedy with a Cabinet slot after the election, if he can win confirmation in the Republican-controlled Senate.

There are also subsets of conservatives who were drawn toward Kennedy’s position on food and the pharmaceutical industry. The conservative journalist Rod Dreher published his book Crunchy Cons in 2006, which highlighted from a traditionalist perspective some of the health and lifestyle choices popular in these circles. Vaccine skepticism became more of a right-leaning than left-leaning phenomenon during COVID-19, despite Operation Warp Speed being a Trump administration initiative. 

A key Senate panel voted along party lines to advance Kennedy’s nomination on Tuesday. This included Sen. Bill Cassidy (R-LA), who appeared inclined to oppose Kennedy during the confirmation hearings. Cassidy is up for reelection in 2026 and could face a primary challenger.

Ten years ago, it would have been easy to imagine a Democratic president nominating Kennedy to a government position and him eliciting unanimous Republican opposition. 

It did not look like smooth sailing for Kennedy even with Trump submitting his nomination to a Republican Senate majority. Even if Trump needed Kennedy’s voters to win, which some Republicans dispute, most red-state GOP senators don’t. 

But Republicans may fall in line behind even the least conventional of Trump’s nominees. Tulsi Gabbard, a former progressive Democratic congresswoman who is Trump’s choice for director of national intelligence, is also thought to have won crossover votes for the 2024 GOP presidential ticket. Hawkish Sens. Tom Cotton (R-AR) and Lindsey Graham (R-SC), Trump allies who might have opposed her nomination under different circumstances, have both announced their support. So has Sen. Susan Collins (R-ME), one of the three Republicans to vote against Defense Secretary Pete Hegseth.

Kennedy has softened or disavowed some liberal positions to win Republican votes, especially vowing to adhere to the Trump administration’s general opposition to elective abortion.

Meanwhile, Pence’s rift with Trump has hurt his influence among Republicans. He sought the 2024 GOP presidential nomination but polled in the single digits and dropped out before the first primary or caucus. He has since sought to push back against Trump’s populist influence over the party, but the fight looks one-sided at the moment.

Kennedy can only afford three Republican defections to win confirmation with Vice President JD Vance’s tiebreaking vote. His nomination will soon proceed to the Senate floor.