WASHINGTON, May 19, 2026 — The U.S. Senate advanced an Iran war powers resolution Tuesday for the first time after seven previously failed attempts, and the vote that finally broke the deadlock came from a senator whose political fate had just been sealed by the very president the resolution targets. Sen. Bill Cassidy of Louisiana, voting yes on a war powers measure for the first time since the Iran conflict began, did so just days after President Donald Trump endorsed a primary challenger who knocked him out of contention for his own Senate seat.
The vote marked the first time Cassidy supported advancing a war powers resolution. It came days after he failed to win enough support to advance to a runoff in the Louisiana GOP Senate primary, where Trump endorsed one of his opponents. For months, Cassidy had been a reliable vote against the Democratic-led resolutions, siding with his party each time the measures came to the floor. His reversal on Tuesday provided the margin that made history.
The resolution now advancing through the Senate was introduced by Sen. Tim Kaine of Virginia and co-led by Senate Minority Leader Chuck Schumer and a coalition of Democratic senators. It directs the president to “remove the United States Armed Forces from hostilities within or against Iran, unless explicitly authorized by a declaration of war or a specific authorization for use of military force.” Democrats had brought the measure or nearly identical versions of it before the Senate repeatedly since the war’s opening strikes in late February, losing each time along near-party-line votes.
In a statement explaining his reversal, Cassidy pointed not to any personal grievance with Trump but to what he described as the administration’s failure to keep Congress informed. “While I support the administration’s efforts to dismantle Iran’s nuclear program, the White House and Pentagon have left Congress in the dark on Operation Epic Fury,” Cassidy said. “In Louisiana, I’ve heard from people, including President Trump’s supporters, who are concerned about this war. Until the administration provides clarity, no congressional authorization or extension can be justified.”
The final tally was 50-47. Joining Cassidy in crossing party lines were Sens. Susan Collins of Maine, Lisa Murkowski of Alaska, and Rand Paul of Kentucky. Sen. John Fetterman of Pennsylvania was the sole Democrat to vote against the measure. Three Republicans — Sens. John Cornyn of Texas, Tommy Tuberville of Alabama, and Thom Tillis of North Carolina — did not vote, tipping the scales in Democrats’ favor for the first time since they began bringing war powers resolutions related to Iran.
The war at the center of the resolution has now stretched more than 80 days. Trump announced major combat operations against Iran on Feb. 28, with massive joint U.S.-Israeli strikes targeting military, government, and infrastructure sites. The War Powers Resolution of 1973 requires presidents to remove U.S. forces from any conflict that Congress has not authorized within 60 days. Trump hit that deadline on May 1 but sought to sidestep it by claiming the conflict was effectively over, even as the United States continued to enforce a naval blockade of Iran.
Kaine, who has anchored the Democratic legislative effort on war powers since the conflict began, said the current ceasefire period made congressional action not only appropriate but urgent. “If we’re in a ceasefire where we are trying to find a diplomatic path forward, rather than precipitously start a bombing campaign again, this is exactly the time where Congress should be having a debate about the rationale for the war,” Kaine said on the Senate floor before the vote. After the tally was confirmed, Kaine said: “President Trump’s deeply unpopular war of choice in Iran has imposed a tremendous cost on the American people — including deaths and injuries of our servicemembers and soaring gas prices. I’m grateful that today, enough of my colleagues stood up for the Constitution and listened to their constituents.”
Schumer declared after the vote: “Vote by vote, Democrats are breaking through Republicans’ wall of silence on Trump’s illegal war. For more than 80 days, Trump has dragged America into a costly, chaotic conflict with no plan, no objective, and no legal authority. Today proved our pressure is working: Republicans are starting to crack, and momentum is building to check him. We are not letting up.”
The resolution’s path forward, however, remains uncertain even within the chamber that just advanced it. Under Senate rules, a floor vote on the underlying resolution must occur within three calendar days — giving Republicans more than enough time to get absent senators back to Washington. If Cornyn, Tillis, and Tuberville all return and vote as they have in the past, the measure would fail 50-50. It would then still need to pass the Republican-controlled House and survive an almost certain presidential veto before taking effect. No war powers resolution has ever overcome a presidential veto.
The political backdrop surrounding Tuesday’s vote added a dimension that no procedural timeline could fully contain. Trump’s decision to actively campaign against Cassidy in Louisiana set in motion a chain of events that delivered Democrats their first Senate win on Iran war powers after eight consecutive defeats. Cassidy had also voted to support an Iran war powers resolution in 2020, making his recent string of votes against the measures under Trump a chapter that closed as abruptly as it began — ending with the same senator, now with nothing left to lose, providing the vote that no one on either side had managed to secure for nearly three months of war.