President Trump has spent recent weeks endorsing primary challengers to Republican senators who crossed him, a political strategy that may feel satisfying but carries a steep cost. If Justice Clarence Thomas or Justice Samuel Alito steps down, Trump could find himself short of the votes he needs to confirm a replacement.

The arithmetic is straightforward. Republicans hold 53 Senate seats. A Supreme Court confirmation requires 50 votes, with Vice President JD Vance available to break a tie. That means Trump can lose three Republican senators and still get a nominee through. Four defections, and the nomination fails.

As Newsweek reported in a detailed analysis, at least four GOP senators, Susan Collins of Maine, Lisa Murkowski of Alaska, Thom Tillis of North Carolina, and Bill Cassidy of Louisiana, have each broken with the president on major votes and could plausibly refuse to support a conservative Supreme Court nominee. Collins and Murkowski have a long track record of concern over judicial nominees. Tillis has announced he will not seek reelection in 2026, freeing him from any political pressure. Cassidy just lost his Louisiana primary on May 16 to Trump-backed Julia Letlow, giving him zero incentive to do the White House any favors on his way out the door.

The revenge tour's hidden price tag

Trump's campaign against disloyal Republicans has been effective as raw politics. Cassidy is finished. Ken Paxton, the Texas attorney general endorsed by Trump, faces John Cornyn in a May 26 Republican primary runoff. But every scalp comes with a cost to the confirmation math.

Cornyn until recently chaired the Senate Judiciary Committee, the body that vets every Supreme Court nominee before a full Senate vote. Trump endorsed Paxton over him. Senator Collins responded with open frustration.

"I don't understand. He [Paxton] is an ethically challenged individual. John Cornyn is an outstanding senator and merited the president's support."

Collins is running for reelection in a state where Trump's net approval sits at negative 17. She has no political reason to cast a difficult vote for a conservative nominee, and now she has a personal reason to resist.

Jim Kessler, an analyst at the centrist think tank Third Way, laid out the problem bluntly. He told Newsweek that Collins, Murkowski, and Tillis were already likely "no" votes on any Supreme Court pick, and that Trump's treatment of Cornyn only deepened the fracture.

"Revenge is a two-way street. All the politicians that he's gone after are either finished with their career or they hope to have a second start by being someone who took Trump on. So somebody like John Cornyn, who's been a Republican loyalist his entire life and was stabbed in the back by Trump."

Kessler added flatly: "I don't think the votes are there for that."

Thomas and Alito show no signs of leaving

For now, this is a hypothetical crisis. Neither Thomas nor Alito has signaled any intention to retire. Thomas has told associates he "continues to love the work." Alito has hired law clerks for the next term and has a book scheduled for publication in October, one day after the new Supreme Court term begins. Those are not the actions of men planning to step aside.

Thomas, who remains one of the Court's most consequential voices, recently authored the opinion in an 8-1 ruling on Cuba property claims, writing for a near-unanimous bench. He has also pushed the Court in ambitious directions, including urging colleagues to rethink the Voting Rights Act's role in redistricting. These are not the moves of a justice in retreat.

Alito's health did draw attention after he was hospitalized briefly in March for dehydration. But his continued hiring and publishing schedule suggest he has no plans to create a vacancy.

Trump, for his part, told Fox Business in April that he was "prepared" to nominate two or three justices if seats opened. He has mentioned Senator Ted Cruz and Judge Aileen Cannon as possible picks. Whether those names were trial balloons or serious candidates remains unclear.

The 2026 Senate map makes the clock tick louder

If Trump cannot confirm a justice now, his window may close entirely. A year ago, Republicans expected to expand their Senate majority in 2026. That confidence has evaporated.

Republican strategist Mike Madrid described the shift in stark terms:

"A year ago, nobody ever believed that the Democrats would be within striking distance of getting a majority in the Senate. And now it's, you know, it's a coin toss. It's as likely as that it's not. That jeopardizes the entire Trump agenda. And of course, Supreme Court justice becomes a big part of that consideration."

Democrats need to flip four seats to take control. Trump's approval ratings in battleground states offer them openings. In Michigan, his approval stands at negative 14. In Texas, a state he won by 14 points in 2024, his approval has slipped to negative 3. Matt Klink, president of Klink Campaigns, warned that low approval numbers could drag down Republican candidates across the board.

"The danger for Republicans is that Trump's approval becomes the emotional shortcut voters use to make decisions in races they otherwise haven't fully engaged."

If Democrats gain control of the Senate by January 2027, any Supreme Court vacancy would become nearly impossible to fill with a conservative nominee. The entire confirmation calculus changes.

A self-inflicted wound on the right's biggest prize

The conservative legal movement has spent decades building toward a Supreme Court that takes the Constitution's text seriously. Thomas and Alito have been central to that project. Both joined the majority in cases that reshaped American law, from the Court's recent limits on Voting Rights Act redistricting claims to its handling of regulatory power and religious liberty.

Replacing either justice with a nominee of equal caliber would be a generational achievement. Failing to do so, because of avoidable feuds with members of your own caucus, would be a generational failure.

Cassidy voted to convict Trump in his second impeachment. He voted with Collins and Murkowski to force Senate debate on Trump's Iran war powers. He announced opposition to White House ballroom funding in the budget reconciliation bill. None of that made him a liberal. It made him a senator Trump wanted gone. And now Cassidy is gone, with no reason to help the president on his way out.

Tillis, similarly freed from electoral pressure after announcing he won't run again, has opposed several administration judicial nominees. Collins and Murkowski have voted against conservative Supreme Court picks before. The pattern is not new. What is new is that Trump has actively antagonized all of them at the same time.

The president called Cassidy "a sleazebag, a terrible guy, who is bad for Louisiana." Whether or not that description is fair, it is not the language of a leader building a coalition to confirm the most important appointments of his presidency.

The stakes dwarf the grudge

There is nothing wrong with holding Republican senators accountable. Primary challenges are a legitimate tool. But tools have consequences, and the consequence here is measurable: four potential defections in a chamber where three is the maximum.

Trump has the right nominees in mind. He has the constitutional authority. He may even have the opportunity, if Thomas or Alito decides the time is right. What he may not have, because he chose not to preserve it, is the Senate math.

Conservatives who care about the Court should hope the president finds a way to count to 50 before the chance disappears. The left will not give him a second one.