The Senate on Thursday passed a resolution to block President Donald Trump from further attacks on Iran after a bipartisan group of lawmakers worked together to defeat multiple Republican amendments designed to weaken or kill outright the legal force of the measure.

Senators passed, as amended, the legally binding measure from Sen. Tim Kaine, D-Va., by a vote of 55-45. That number was four affirmative votes more than the vote the day before to begin debate on the resolution. It included votes in favor by eight Republicans: Lamar Alexander of Tennessee, Bill Cassidy of Louisiana, Susan Collins of Maine, Mike Lee of Utah, Jerry Moran of Kansas, Lisa Murkowski of Alaska, Rand Paul of Kentucky and Todd Young of Indiana.

The privileged resolution, offered under the 1973 War Powers Act, would require Trump to immediately end any hostilities against Iran and its officials without a vote of Congress. And it comes amid continuing fears about the prospects for war after the early January targeted drone killing by the United States of Iran’s top military commander, Maj. Gen. Qassem Soleimani.

“It has been a very collaborative process with a lot of dialogue, a lot of listening, a lot of changes in amendments back and forth since early January,” Kaine said, noting that the issue of congressional authorization of war is personally important to him since he has a child in the military. “When I came here in 2012, I started to look for colleagues on both sides of the aisle and both houses who would stand for the proposition that war is the most solemn responsibility we have and it cannot be outsourced to anyone.”

[Senate votes to begin debate on resolution limiting Trump’s war powers on Iran]

The resolution says that nothing in its language may be construed to prevent the president from using military force to defend the U.S. against imminent attack.

William Ruger, the vice president of research and policy for the center-right Charles Koch Institute, said polling shows majorities of Americans are opposed to deepening U.S. military engagement in the Middle East.

“The idea of getting into another war in the Middle East is something they are very wary of,” said Ruger, an Afghanistan war veteran. “They would also like to see a broader debate about these issues, and that is one of the important things about Congress playing a role … it slows the process down, it allows for our Republican and our Democratic institutions to play their proper role.”

The measure now goes to the House, where it is expected to easily pass. However, President Donald Trump is expected to veto the resolution, and supporters of constraining his ability to attack Iran lack the two-thirds vote necessary in both chambers to overturn such a veto.

GOP amendments defeated

The Senate floor action Thursday was notable for displaying the rare policy area in which GOP members are still willing to differentiate themselves in notable numbers from the wishes of the president.

Sens. Tom Cotton, R-Ark., Marco Rubio, R-Fla., and Dan Sullivan, R-Alaska, each offered unsuccessful amendments aimed at weakening or killing the resolution. All were defeated thanks to the votes of a handful of their GOP colleagues who sided with Democrats in voting against the amendments.

Cotton offered an amendment that would have carved out an exception in the resolution for military operations against “entities designated as foreign terrorist organizations.” The Arkansas Republican freely acknowledged he wanted to allow the administration to attack the Islamic Revolutionary Guard Corps, which the Trump administration added to the State Department’s foreign terrorist organization list last spring.

The Iranian Revolutionary Guard Corps, which Soleimani headed, is the most potent branch of Iran’s military and under his leadership assiduously worked to deepen and expand ties to powerful militia groups across the Middle East, including Hezbollah in Lebanon and Shiite militias in Iraq.

“This is indeed only about the Islamic Revolutionary Guard Corps,” Cotton said. “The vote here is simple. Do you want to stand with our troops, hundreds of whom have died at the hands of Iran, or do you want to vote to be a lawyer for Iranian terrorists?”

Kaine warned that Cotton’s amendment would set a dangerous precedent by allowing military action against any entities on the foreign terrorist list, which is controlled by the executive branch. There are currently about 69 groups on the list, including the Irish Republican Army and the Kurdistan Workers Party, he noted.

“The FTO list has never been a war authorization. It is created by the administration. It adds the names to it,” Kaine said in calling for a motion to table the amendment. “This would basically destroy the underlying bill by allowing a president to add to the FTO list, not come to Congress and then take military action.”

The Cotton amendment was tabled by a vote of 54-46, with Alexander, Cassidy, Collins, Lee, Murkowski, Paul and Young voting against the measure.

Rubio’s amendment would have added language to the findings section of the resolution asserting that the U.S. military is “not currently engaged in hostilities, as contemplated by the War Powers Resolution, against Iran.”

Kaine argued that the events of late December and early January, which saw fatal rocket and missile attacks by both the United States and Iran against each other’s forces and aligned partners, constituted hostilities as conceived by the War Powers Act. That includes the Jan. 8 ballistic missile attack by Iran on the Al-Assad Air Base in Iraq, which resulted in concussions and other brain injuries for roughly 100 U.S. troops deployed there.

“The War Powers Act has a definition of what armed conflict and hostilities are, and it is clear that Congress was meant to be able to file this exact motion, either during armed conflict or even before armed conflict, if it was imminent,” Kaine said. “I would argue that the 100 servicemembers who were suffering from head injuries and the American contractor who was killed is definitely proof that there are hostilities.”

The Rubio amendment was defeated, 54-46. And Sullivan’s amendment, which would have added clarifying language stating the president can use military force to defend military personnel, bases and diplomatic facilities, was narrowly defeated, 51-49.

Lee spoke against the amendment, saying it would introduce “ambiguity” into the resolution.

Senators did vote, 64-34, to adopt an amendment from Sen. Ted Cruz, R-Texas, that adds language to the findings section praising Trump, the U.S. military and the intelligence community for the Jan. 2 drone strike that killed Soleimani.