Voters in Louisiana head to the polls Saturday in a Republican Senate primary that has become the fight of Bill Cassidy’s political life, with polling and prediction markets reinforcing just how difficult his path to re-election has become.
Cassidy is facing the most serious challenge of his Senate career because his 2021 vote to convict President Donald Trump in the impeachment trial never stopped reverberating inside Louisiana’s Republican electorate.
Key Points To Know
- Louisiana Republicans vote today, May 16, in what has been termed a “semi-closed” party primary for U.S. Senate, pitting Cassidy against Julia Letlow and John Fleming in a contest shaped by Trump’s push to oust the incumbent.
- Public polling has been fragmented, but recent surveys point to a consistent pattern: no candidate above 50 percent and Cassidy trailing both in the first round and in hypothetical runoffs.
- Prediction markets suggest Letlow has pulled clear of the field, with traders assigning her a dominant lead over Fleming and Cassidy, even as polling continues to show a more fragmented and uncertain race.
- A sitting senator is at risk of being knocked out before November, and the result tests whether Trump-loyalty politics can topple an incumbent who broke with the president.
- Whoever wins the GOP nomination is heavily favored in the general election in deep-red Louisiana, so today’s contest is effectively the decisive contest for the seat.
- Today’s primary is also the first major federal test in Louisiana under the state’s new “semi-closed-party” primary rules, which can amplify base-driven outcomes in low-turnout contests.
A Primary Shaped By Trump And A New Election System
Louisiana is holding party primaries for U.S. Senate today, with any needed runoff scheduled for June 27.
Unlike Louisiana’s long-running “jungle primary” tradition, eligible voters are now funneled into party-specific ballots for certain offices, including the U.S. Senate.
No-party voters can choose a party ballot at the polls but are then locked into that choice through a runoff, a detail that matters in a two-step contest where coalitions can harden fast.
That rules shift lands in the middle of a Republican civil war framed around allegiance to Trump.
Letlow entered the race with Trump’s backing and has run as the candidate most aligned with his agenda, while Fleming has pitched himself as a more reliably conservative option in a three-way field.
Cassidy, for his part, has argued he can work with Trump’s administration now while still defending his impeachment vote as a matter of principle—an argument that asks a lot of a primary electorate where Trump remains popular.
The Central Vulnerability: The Impeachment Conviction Vote
The core political fact hovering over today is simple: Cassidy voted to convict Trump after the January 6 Capitol Hill riots, and Trump has not let it go.
In the closing stretch, Trump publicly urged Louisiana Republicans to vote Cassidy out, a message that effectively nationalizes what would otherwise be a local, personality-and-turnout contest.
In a normal cycle, incumbency, donor networks, and name recognition create a high floor.
Closed primaries can lower that floor by narrowing the electorate to the most habitual and partisan voters—exactly the group most responsive to elite cues like endorsements and grievance politics.
That is one reason analysts are watching whether Cassidy can even make the runoff, not merely whether he can win it.
What The Polling Shows
Public polling has not been uniform—different firms have told different stories at different moments—but the most recent, higher-profile releases share a common theme: no one is consistently clearing 50 percent, and Cassidy is routinely fighting from behind.
These surveys were conducted before Election Day and do not reflect real-time vote counts or any exit polling from Saturday’s vote.
In a Quantus Insights survey of 1,015 likely voters, conducted between May 6 and 7, 2026, with a margin of error of plus or minus 3 percent at the 95 percent confidence interval, on the first-round ballot test, Letlow led with 42 percent, followed by Fleming at 30 percent and Cassidy at 20 percent, with 7.5 percent undecided and 1.7 percent for a minor candidate.
The same Quantus survey tested runoff matchups—useful in Louisiana’s two-round reality.
In a hypothetical runoff between Cassidy and Letlow, Letlow led 63 percent to 23.4 percent (with 13.6 percent undecided) among a weighted sample of 880 respondents.
In a Cassidy–Fleming runoff, Fleming led 55.1 percent to 24.6 percent (20.3 percent undecided) among a weighted sample of 816.
The decisive matchup, however, is between Letlow and Fleming in a potential runoff, where Letlow’s lead narrows to six percentage points: 45.4 percent to 39.6 percent, with 15.0 percent undecided.
But for the incumbent, these are not small margins; they imply Cassidy’s problem is not merely first-round fragmentation but potential head-to-head weakness.
A Republican-sponsored Fabrizio, Lee & Associates survey for the Accountability Project of 600 likely Republican primary voters, conducted between May 4 and 5, with a plus or minus 4 percent margin of sampling error at the 95 percent confidence interval, showed Letlow at 32 percent, Cassidy at 26 percent, Fleming at 21 percent, with 19 percent undecided.
It also included an “informed endorsement” question: among those who had not yet voted, informing respondents that Trump “fully endorsed” Letlow moved the ballot to 38 percent Letlow, 23 percent Cassidy, and 20 percent Fleming, with 17 percent undecided.
An Emerson College poll, conducted from April 24 to 26, sponsored by KLFY/Nexstar, surveyed 500 likely Republican primary voters and reported a plus or minus 4.3 percent margin of error.
In that snapshot, Fleming led narrowly at 28 percent, Letlow was at 27 percent, and Cassidy trailed at 21 percent, with 22 percent undecided.
Emerson also found Cassidy with a markedly negative standing among likely GOP primary voters (30 percent favorable, 49 percent unfavorable).
Taken together, these polls describe an electorate that is still splintered but not randomly so.
Letlow and Fleming each have plausible paths to first place in round one; Cassidy’s path depends on surviving the first cut in a contest where undecideds and turnout composition can decide which two advance.
What The Markets Are Pricing In
Prediction markets are pricing the race as if Letlow has separated from the pack, even though polling still shows a meaningful spread of outcomes.
On Polymarket’s “Louisiana Republican Senate Primary Winner” market, Letlow was priced around 76 percent at the time of writing, Fleming about 22 percent, and Cassidy about 3 percent, with roughly $286,114 in total volume displayed on the market page.
Kalshi’s “Louisiana Republican Senate primary: first round winner” market similarly implied a Letlow advantage, listing Letlow at about 94 percent at the time of writing, Fleming at 1 percent, and Cassidy at 7.3 percent, with about $36,699 in volume shown.
Prediction markets aggregate what traders believe will happen, not what “must” happen.
They can be fast at processing new information (polls, endorsements, late-breaking narratives), but they can also be distorted by thin liquidity, herding, or participants trading on sentiment rather than ground truth.
They are best treated as one more indicator—alongside polling and on-the-ground dynamics—not a substitute for votes and do not reflect real-time exit polling data.
What Happens Next
Polls are set to close across Louisiana at 8 p.m. local time (9 p.m. ET) on Saturday, with initial results expected shortly after and fuller returns coming into focus over the following hours.
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