Sen. Bill Cassidy (R-LA) joined with Democrats to vote for a procedural motion advancing legislation that would end U.S. military operations against Iran, allowing the war powers resolution to move forward on Democrats’ eighth such attempt since the war began.

Cassidy joined three other Republicans — Sens. Susan Collins (R-ME), Lisa Murkowski (R-AK) and Rand Paul (R-KY) — in voting for the procedural motion, which was approved by a 50-47 vote. Sen. John Fetterman (D-PA) voted against the motion.

The passage of the motion will now tee up further debate and an additional vote on the resolution itself, at a time to be determined. The Senate is set to depart for a Memorial Day recess this weekend, and floor time this week is expected to be focused on a reconciliation bill funding immigration enforcement, among other issues.

Cassidy’s vote came days after he lost his primary race to a challenger backed by President Donald Trump. He’s been supportive of the Iran war to this point, but has also been critical of the administration and has voiced the need to assert congressional power, particularly in the wake of his election loss.

He emphasized to reporters on Monday evening the need to rally support from traditional U.S. allies to address the situation in the Strait of Hormuz.

“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 on X. “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 result came about in part due to absences by Sens. John Cornyn (R-TX), Thom Tillis (R-NC) and Tommy Tuberville (R-AL). Had they been present and voted as they have in the past, the vote would have been tied, allowing Vice President JD Vance to cast a tie-breaking vote and reject the motion.

Yet, some of those votes may not be guaranteed when the resolution itself comes to the floor.

Tillis, who is retiring, has repeatedly bucked Trump and his party on a range of issues. Cornyn has been strongly supportive of the war, but Trump on Tuesday endorsed his primary opponent, Texas Attorney General Ken Paxton, likely setting Cornyn on the road to defeat in his primary race.

Cornyn announced on X shortly after the vote that he would be canceling campaign events in Texas on Wednesday and heading back to Washington to vote on Republicans’ reconciliation bill.

However, earlier this year, several Republicans voted with Democrats to advance a similar motion on a war powers resolution relating to Venezuela, but most of them flipped their votes under pressure from the administration and Republican leadership, ultimately blocking final passage of the resolution.

The House could pass a war powers resolution as well this week, depending on attendance. A previous vote last week was tied, 212-212, but Rep. Jared Golden (D-ME), the sole Democrat to vote against the resolution, said he would vote for a future resolution.

Even if the resolutions pass, they can still be vetoed by Trump.