The chamber voted 49-50 on the resolution, the latest to call for an end to the war.
All but four Republicans voted against the measure despite concerns that GOP candidates will face fallout in November’s midterm elections from the war’s economic costs.
The Republicans who voted for the resolution were Sens. Thom Tillis of North Carolina, Maine’s Susan Collins, Lisa Murkowski of Alaska and Rand Paul of Kentucky. Sen. John Fetterman of Pennsylvania was the lone Democrat to vote against it.
Sen. Angela Alsobrooks, a Maryland Democrat, did not vote despite having been in the Senate earlier Thursday. Alsobrooks has previously voted for similar resolutions. But if she had again voted that way on Thursday, the resolution still would have failed.
“Senator Alsobrooks has voted 13 times to end the war in Iran. Unfortunately, she was dealing with an urgent family matter during today’s vote so was unable to cast her fourteenth vote to end the war in Iran,” Alsobrooks’ spokesperson Meredith Happy said in a statement to CNBC. “She believes every day that this war rages on, Americans are paying for it at the gas pump and the grocery store—and too many American service members have paid with their lives. She continues to urge this President to end this war once and for all.”
An affirmative vote on the measure, known as a War Powers Resolution, would have directed President Donald Trump to remove U.S. troops from hostilities in Iran unless Congress explicitly approves the war.
The Senate has voted repeatedly on similar measures since the war began, approving one of them. The White House has effectively ignored that vote, arguing that the War Powers Act is unconstitutional.
The measure voted on Thursday, which like the one adopted was a so-called “concurrent resolution,” did not carry the force of law and is never signed by the president, making the vote largely symbolic even if it had passed.
The Democratic leaders of the legislative push, however, argue that the Constitution vests authority to declare war in Congress, not the executive branch, and that the president must abide by their disapproval whether or not he signs it.
“The president right now is in violation of the Constitution and the War Powers Act and the concurrent resolution that we’ve already passed,” said Sen. Tim Kaine, D-Va., who has led a number of the votes to end the war.
“We shouldn’t have to do a second one because the president should follow the law, but we are doing a second one on the theory that maybe after a number of months more people will join us, the American public is even more deeply opposed to this war.”
The measure passed the House in July and faced just a 50-vote threshold to clear the Senate. Democrats have seen an uptick in Republican support in recent votes to end the war, as the administration has blown through timelines to seek congressional approval for the conflict.
The war has also created a challenging political environment for incumbent Republicans, who could lose control of the House and Senate in the midterm elections that loom less than six weeks away.
Lawmakers are set to hit the campaign trail for nearly all of October, and will need to explain to voters what they are doing to bring down prices.
“There are a lot of good things we can talk about; the problem is what you did for me recently doesn’t even hardly count,” said Sen. Kevin Cramer, R-N.D., when asked about how Republicans can message to economically anxious voters. “The other thing that we get to talk about … is that at least we’re not socialists.”