The Louisiana Republican Senate primary race remains a three-way battle heading into Saturday’s primary, but prediction markets are still definitively suggesting incumbent Sen. Bill Cassidy will see his tenure end.
The race has lots of national attention, plenty of drama, and a market that still refuses to buy any incumbent advantage. While Cassidy enters Saturday’s primary with the one thing challengers can’t fake in a race like this, incumbency, President Donald Trump’s open hostility toward him is making its influence known in the prediction markets. Cassidy is one of the Senate Republicans who voted to impeach Trump after Jan. 6, 2026, and that vote has hung over him for years like a political debt that never quite gets paid off.
Representative Julia Letlow has tried to turn that anger into a real primary challenge with Trump’s endorsement. Meanwhile, John Fleming has tried to make the race about the base’s appetite for a more reliable Trump-aligned conservative. Despite national headlines this week like the Wall Street Journal’s “Julie Letlow is Trump’s Big Midterms Gamble,” her campaign appears to be working as Cassidy is trending in the single-digits to win Saturday on both Kalshi and Polymarket.
If no candidate receives 50% during Saturday’s election, the top two head to a runoff. That could set up a similar battle like that in the Texas GOP Senate race between incumbent Sen. John Cornyn and Ken Paxton.
Cassidy still has the incumbency edge
Cassidy is still behaving like the incumbent in the way that matters most. He’s holding together enough of a Republican coalition to keep the national narrative from flipping on him. The latest polling is messy, but it still gives Cassidy a live path, especially in the cross-pressure zone where Republican voters may dislike his Trump vote but still recognize the advantages of a sitting senator with name recognition, money and the ability to survive a divided field.
The president can dominate the conversation, but that does not automatically mean an insurgent cashes in. In Indiana, Trump-backed candidates showed the power of the brand in state-level contests. But Kentucky Rep. Thomas Massie has shown the other side of the equation. Sometimes an incumbent with a distinct brand and a deep local following can absorb the pressure, even when the air is full of loyalty tests.
Cassidy is trying to do the same thing Massie is doing. That is to survive during a purge narrative by leaning on local familiarity, constituent service, and the practical reality that voters often like the benefits of an incumbent even when they approve of the attack ads.
Trump’s shadow is still the whole race
Of course, none of that changes the fact that Trump is the dominant political force in modern national politics. His endorsement of Letlow gives the race its central question: Can the anti-Cassidy vote consolidate enough to beat a sitting senator who has spent years trying to outlast the blowback from one vote?
The bigger point is that this race sits in the same category as the Massie primary in Kentucky. Trump can move the conversation and help a challenger, but markets are also learning to ask whether the incumbent has enough of a brand to survive the loyalty test. In Louisiana, Cassidy’s brand is not popular in every Republican corner, and that appears to be hurting him in the markets.
Louisiana Senate prediction markets read
Letlow jumped out to a commanding lead in the markets when she entered the race in January. She has maintained that lead through, up to 79% on Kalshi and 72% on Polymarket. Not much has changed in the last month, except for about $100K in volume on both platforms, up to $294K on Kalshi and $272K on Polymarket.
Fleming sits at 19% on Kalshi and 17% on Polymarket, while Cassidy is sitting under 4% on both markets.
The polls show Louisiana Senate race mess
The New York Times polling tracker shows exactly why the markets haven’t swayed majorly. The numbers are competitive but not decisive, but the polls don’t like Cassidy’s chances either.
Three Quantus Insights polls from earlier this month show:
- Fleming +31
- Letlow +12
- Letlow +6
Cassidy is third in the polls, around 20% to 25%, with a solid chunk of undecideds. That is not the shape of a clean anti-incumbent wave. That is the shape of a fragmented primary where the anti-Cassidy vote may be real but not necessarily coordinated. That fragmentation is what Cassidy is counting on. Letlow’s Trump endorsement gives her the strongest single lane, but Fleming’s presence gives the anti-incumbent crowd a second lane and makes a first-ballot knockout harder to predict.
Another Trump midterm power test
The Louisiana primary fits the same broader pattern as other Trump-influenced 2026 midterm election races. The former president can ignite a race, but he does not automatically erase incumbency.
That has been part of the lesson in Massie’s Kentucky fight, and it is why Trump-backed strength in Indiana state races matters here too. It shows the base can still be mobilized, but not every Republican target falls just because Trump says so.
Heading into Louisiana’s primary Saturday, Cassidy is still the incumbent, Trump is still the powerful outside voice, and the market is still leaning toward Trump’s influence.
