WASHINGTON, May 19, 2026 — The U.S. Senate advanced a war powers resolution Tuesday aimed at forcing an end to President Donald Trump’s military campaign against Iran, marking the first time the Senate approved moving forward with such a resolution after seven previously failed votes. The breakthrough came by a margin of 50-47 — and the vote that made it possible belonged to a senator who, just days earlier, had been driven out of his own party’s primary by a Trump-endorsed challenger.
Sen. Bill Cassidy of Louisiana had voted against advancing similar Iran war powers resolutions every time they came before the Senate. Tuesday marked the first time Cassidy supported advancing a war powers resolution — and it came just 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. The timing of his reversal was immediately striking to observers on both sides of the aisle, arriving within the same week that Trump’s political intervention effectively ended his Senate career.
Cassidy released a statement explaining his position: “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. 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 resolution Cassidy voted to advance was introduced by Sen. Tim Kaine of Virginia. 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 nearly identical measures to the floor repeatedly since the war began in late February, only to fall short each time along near-party-line votes.
Four Republicans ultimately crossed over on Tuesday — Sens. Susan Collins of Maine, Lisa Murkowski of Alaska, Rand Paul of Kentucky, and Cassidy — joining the bulk of Democrats. Sen. John Fetterman of Pennsylvania was the sole Democrat to oppose 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. Without those three absences combined with Cassidy’s flip, the resolution would not have advanced.
Cassidy also voted to support an Iran war powers resolution in 2020, making his recent string of “no” votes under Trump a notable departure from his earlier record on the issue. His return to the pro-resolution column, under circumstances shaped so directly by Trump’s political targeting of him, immediately became the defining story of a vote that had otherwise seemed destined to fail like the seven before it.
The conflict at the center of the resolution has now stretched well past its legally significant deadline. 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. The war began Feb. 28 with massive joint U.S.-Israeli strikes targeting military, government, and infrastructure sites in Iran.
Senate Minority Leader Chuck Schumer framed the vote as a sign that the months of repeated losses were finally yielding results. “Vote by vote, Democrats are breaking through Republicans’ wall of silence on Trump’s illegal war,” Schumer said. “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.”
Kaine, who has led the Democratic legislative push on the Iran war for months, reflected on the breakthrough with cautious optimism. “It sort of feels like the momentum is slowly, not fast enough for me, but moving our way, and that’s really positive,” Kaine told reporters after the vote. He had predicted before the tally that a Republican would eventually join — he just hadn’t known when. “I didn’t know that we would get an additional vote last week when Murkowski became the third Republican to support advancing the resolution,” Kaine said ahead of Tuesday’s vote. “But I do know this: I know what we are all hearing from our constituents, and that is, they are deeply opposed to this war.”
Despite the historic nature of the procedural advance, the resolution faces a difficult road before it could carry any force. It is not yet guaranteed to pass even within the Senate itself: if Cornyn, Tillis, and Tuberville all return to vote on final passage as they have in the past, the measure would break 50-50 and fail. Even if the resolution eventually clears the full Senate, it must also pass the Republican-led House and garner two-thirds majorities in both chambers to overcome an expected presidential veto. No war powers resolution has ever survived a presidential veto.
But the political symbolism of Tuesday’s vote cut through the procedural uncertainty. A senator who had spent months standing with Trump on the Iran war, only to have Trump work to end his Senate career, cast the vote that gave Democrats their first Senate win on the issue after eight attempts. As one congressional reporter put it simply: the eighth time turned out to be the charm.