On Jan. 31, during the annual convention of the National Association of Black Journalists in Chicago, the former president questioned whether Vice President Kamala Harris, the presumptive Democratic presidential nominee, was black rather than Indian. Reporters scurried to find GOP pols for comment, and by 6:07 p.m., a knot of them formed a semicircle around Sen. Bill Cassidy (R-LA), who had walked off the Senate floor into a white marble hall that faces the Supreme Court.

Until 2021, Cassidy may have been best known for the healthcare legislation he sponsored with fellow Sen. Lindsey Graham (R-SC), a bill that would have repealed Obamacare and returned control of Medicaid to the states. Now Cassidy has a reputation for an independent streak: He has been both a critic of the former president and a dissenter from his agenda.

Cassidy voted to convict Trump after the Jan. 6 Capitol riot, one of only seven Republican senators to have done so. He said last year that Trump should drop out of the 2024 presidential race. After Trump described some illegal immigrants as “animals” in March, Cassidy described Trump’s words as “dehumanizing” on NBC News’s Meet the Press.

If any conservative Republican senator would criticize Trump, Cassidy would. A practicing gastroenterologist, the 66-year-old is fit and trim with a shock of thick, grey hair, the sort of man whom you can imagine telling the portly Trump to lay off the Big Macs. Yet Cassidy balked.

He insisted he was ignorant of Trump’s latest outrage despite that he makes a living partly by being sensitive to public opinion in general and to Trump’s in particular. “I haven’t seen the full transcript of his remarks, and I would want to see those,” Cassidy insisted.

Did Cassidy see Trump’s comments?

“I don’t even own a TV,” Cassidy protested before he allowed with a nervous chuckle that he wasn’t completely cut off from the modern world. “The only thing I have is the MLB app, to check baseball scores.”

Cassidy’s opposition to Trump has not wavered. Last month, he stayed home in the Bayou State instead of attending the Republican National Convention in Milwaukee. He still hasn’t endorsed Trump for president, although he said he will vote for whichever Republican appears on the presidential ballot this fall.

Cassidy’s brand of opposition to Trump is unique. He hasn’t attempted to throw Trump out of the party in the manner of former GOP Reps. Liz Cheney and Adam Kinzinger. Nor is he a centrist like fellow Sens. Mitt Romney (R-UT), Lisa Murkowski (R-AK), and Susan Collins (R-ME). Instead, Cassidy criticizes Trump on humanitarian grounds: for his enabling of criminal and violent behavior.

Trump has taken notice. “One of the worst senators in the United States Senate is, without question, Bill Cassidy,” Trump wrote on Truth Social, his social media site, in April. The former president went on to assail Cassidy as “wacky,” a “stiff,” a “total flake,” and “disloyal,” even though Cassidy voted with Trump 89% of the time from 2017 to 2021, per FiveThirtyEight.     

Cassidy’s colleagues, too, have noticed. “That’s what he’s known for around here, and that’s who he is: He’s thoughtful,” Sen. Ben Cardin (D-MD) said in an interview at the Capitol on Aug. 1. Collins praised Cassidy for showing “a tremendous amount of integrity (in voting to convict Trump). He weighed the facts of the case, and he took a tough vote.”

Cassidy’s unique brand of opposition to Trump raises two questions. One is, how has Cassidy survived politically? Famously, four of the 10 House Republicans who voted to impeach Trump in 2021 were defeated for reelection. Another four House Republicans who voted to impeach Trump and four Senate Republicans who voted to convict him declined to stand for reelection.

The standard answer is Cassidy benefits from favorable political circumstances. He does not have to face voters again for another two years, in 2026, an eternity in American politics. In addition, in Louisiana in 2020, Cassidy earned a higher share of the vote (59.3%) than Trump did (58.5%).

It’s tempting to think Cassidy benefited from another favorable political circumstance.

For decades, Louisiana operated a “jungle primary” in which the two top finishers faced each other in a runoff race unless one candidate racked up more than 50% of the vote. All registered voters, regardless of political affiliation, are eligible to vote. That reduces the power of ideologically minded voters in both parties, including Trump die-hards.

Yet that system will be gone. Earlier this year, Louisiana abolished its jungle primary in favor of a “closed primary” for certain offices, including Congress, a system that gives partisan die-hards like Trump’s larger sway.

Further, Sens. Tom Cotton (R-AR) and Dan Sullivan (R-AK) enjoyed favorable political circumstances like Cassidy during Trump’s second impeachment trial: They were elected in 2020, gained a larger share of the vote than Trump, and ran in states where unaffiliated voters could vote in the primary. Yet both voted to acquit Trump.

Cassidy had toyed with running for governor and shown interest in running on the No Labels presidential ticket last year. Now he is committed to running in 2026, but he faces a tough fight.

Cassidy himself points out that while he got a higher share of the vote in Louisiana than Trump four years ago, Trump got 27,000 more votes overall. John Feehery, a former spokesman for GOP House Speaker Dennis Hastert, said he agrees Cassidy’s vote to convict Trump could sink his reelection bid. As he wrote in an email, “I don’t think that the vote … was very popular in Louisiana and it will hurt him in 2026 should he decide to run again.”

In short, Cassidy’s vote to convict Trump appears to have been based largely on principle rather than expediency. “If I do the right thing, I can live with myself,” he said in an interview at the Capitol, a statement hard to imagine Trump or many pols making.

The second question Cassidy’s opposition to Trump raises is broader: If Republican senators had followed Cassidy’s lead of disciplined, forthright, and principled opposition to Trump, could they have derailed his march to the nomination?

Cassidy himself said “yes” but declined to elaborate. Collins smiled when asked, but she, too, clammed up. One Senate aide thought the idea intriguing.

If Cassidy fears losing his primary in two years, he has a funny way of showing it. The senator said he expects Trump to win in the fall and to work with him to rewrite the nation’s healthcare laws. The scenario may sound far-fetched, but like Sen. Robert F. Kennedy in 1968, Cassidy dreams things that never were and asks, why not?

Mark Stricherz is a reporter and writer in Washington, D.C.