WASHINGTON D.C. — In 2026, Louisiana’s GOP-controlled legislature replaced the state’s long-standing open primary system with a semi-closed primary for Senate elections. Under the new system, only registered Republicans or unaffiliated voters who chose a GOP ballot could participate in the party’s Senate primary.

Sen. Bill Cassidy, R-La., finished third in the May 2026 Republican primary with roughly 25% of the vote. Cassidy had voted to convict former President Donald Trump in his 2021 impeachment trial. Trump recruited an opponent to run against Cassidy in the 2026 primary. GOP primary voters in Louisiana, Indiana, and Kentucky ousted lawmakers in 2026 who had crossed Trump, including on redistricting.

Louisiana had historically used a majority-vote open primary system for Senate elections, allowing all candidates to appear on a single ballot and permitting any registered voter to participate regardless of party affiliation.

"Americans are exhausted by a culture that treats every disagreement as betrayal. Our constitutional system was designed around debate, persuasion, and compromise," Cassidy wrote on X following his defeat.

John Opdycke, founder and president of Open Primaries, said, "There has been a ratcheting up, a ramping up of both the willingness and the ability of both the Democrats and the Republicans to shape outcomes before the voters get a chance to have a say. And that's really devastating."

Nick Troiano, executive director of Unite America, said, "If you're an elected official, the only threat to your reelection is someone running to your ideological extreme in your primary. And that has had the impact over many years, including this year, of meaning: If you're an independent-minded member of Congress, you're being basically hunted to extinction by the ideological flanks within both political parties."

Nationwide, more than 90% of U.S. House seats are considered relatively safe for one party, and primaries often determine election outcomes in noncompetitive districts. Mid-decade redistricting efforts initiated in 2025 have further reduced the number of competitive House districts.