President Donald Trump is famous for seeking political retribution against his congressional adversaries by supporting candidates who challenge these incumbents in Republican primaries. Two high-profile revenge primaries took place in mid-May, and Trump’s candidates won both handily. The first, on May 16, was the Republican primary in Louisiana in which incumbent Sen. Bill Cassidy (R-La.) faced Rep. Julia Letlow (R-La.), a candidate recruited and endorsed by Trump. In the second, Rep. Thomas Massie (R-Ky.) from Kentucky’s 4th Congressional District lost to the Trump-backed candidate, Ed Gallrein.
Cassidy has been in Trump’s sights since early 2021 when he voted in favor of convicting Trump on the impeachment charges brought by the House. Cassidy, a medical doctor, also mounted strong opposition to the nomination of Robert F. Kennedy Jr. as secretary of Health and Human Services—even though the senator eventually voted to confirm him. Cassidy finished in third place in the primary behind Letlow and State Treasurer John Fleming, who advanced to a June run-off election. Following the five state legislators in Indiana who lost their seats in a similar fashion, Cassidy became the next high-profile elected official to lose his seat to a MAGA candidate. His demise was hastened by the change in Louisiana’s primary rules. They formerly had a blanket primary where anyone, regardless of party affiliation, could vote for a nominee. Under the new rules, only Republicans could vote, cutting independents and Democrats out of the action.
The other “revenge” primary took place May 19 in Kentucky’s 4th Congressional District, where Massie faced a tough battle against first-time congressional candidate Ed Gallrein. Massie has always maintained a reputation as a conservative Republican with an independent and libertarian streak. He drew Trump’s ire in July when he voted against Trump’s signature (and so far only) major piece of legislation: the One Big Beautiful Bill. Soon after, he and Rep. Ro Khanna (D-Calif.) introduced a discharge petition to force a bill to the floor which would release the Epstein files to the public. On March 5, April 16, and May 14, he voted for war powers resolutions that would have directed the president to remove U.S. forces “from hostilities” against Iran. In February, he voted with Democrats to remove tariffs on Canada.
Summarizing his politics before the primary, Massie told WLWT – TV, “90% of the time I vote the way the president and the party would want me to vote…10% of the time, I’m sorry if they’re bankrupting the country, if they’re spying on Americans without a warrant, that’s where I have to deviate from the party.”
Like Cassidy’s primary in Louisiana, Massie’s primary in Kentucky was also closed to anyone who wasn’t a registered Republican. Closed primaries benefit Trump-backed candidates because his MAGA base reliably turns out and independents are barred from voting. Trump-recruited Gallrein—a former Navy SEAL and farmer who had run for state Senate but otherwise had no electoral experience—and not only endorsed him but campaigned for him and sent Defense Secretary Pete Hegseth to Kentucky to do the same, an unprecedented move for a defense secretary since they generally refrain from politics. Gallrein triumphed easily.
There were other primaries on Tuesday, and these were clearly motivated by political retribution. However, it bears noting that in Georgia, Brad Raffensperger, the secretary of state who refused Trump’s request to “find 11,780 votes” after the 2020 presidential election, took a stand—hoping to appeal to the non-MAGA wing of the party. That strategy fell short—Raffensperger failed to advance to a run-off for the Republican gubernatorial nomination.
Primaries are the secret to Trump’s enduring power despite his legal troubles and low approval ratings. Control over his base allows him to discipline his party to such an extent that very few Republicans cross the aisle to vote with Democrats. There are only a few instances in his second term where this has happened. Defections have often occurred during votes on discharge petitions, which automatically bring bills to the floor if they reach the 218-signature threshold. Until this Congress, discharge petitions were rare largely because they challenge leadership’s control over the floor agenda, and rank-and-file members are often reluctant to buck their leaders. But in this Congress, with its slim Republican majority, discharge petitions have succeeded a few times.
The most well-known instances of Republican defections were votes on releasing the Epstein files and votes on Obamacare subsidies. Most recently, three Republicans broke with House Speaker Mike Johnson (R-La.) and the White House, voting for a discharge petition that had languished since July 2025. The bill supports Ukraine and NATO and calls for sanctions against Russia. On votes that did reach the floor, six Republicans voted against the emergency powers Trump used to impose tariffs on Canada. Several war powers resolutions related to Trump’s war in Iran came to a vote in March, April, and May. Each drew Republican defections but none passed. On May 19, however, four Republican senators joined Democrats in passing the most recent war powers resolution.
So far this primary season, Trump has demonstrated that if an elected official crosses him—especially on major issues—he will recruit a MAGA challenger, fund the candidate, campaign for the candidate, and defeat the incumbent in a primary. But his successes may carry hidden costs. Cassidy’s reversal on the war powers resolution vote (he sided with Democrats for the first time) illustrates that Trump now has seven months left with one more Republican senator who feels no obligation to him. The same dynamic applies in the House, where Massie made clear in his election night speech that he will pursue the Epstein files. In another hidden cost of Trump’s victories, candidates who win high-profile races with Trump’s backing will face a steeper challenge in November general elections, where MAGA turnout alone may not be enough.
How effective Trump’s tactics will be in the next Congress remains to be seen, particularly as he becomes a lame duck and Democrats could regain control. Although his support remains strong among Republicans, it has weakened significantly among independents—a crucial swing vote in many elections. Tactics that work in GOP primaries could backfire in general elections, where the voter pool is far broader. Ironically, the very tactics that help him install very conservative nominees in primaries may ultimately cost Republicans in November.
