WASHINGTON ― A striking majority of senators voted Wednesday afternoon to move forward a bill ending U.S. support for a Saudi-led coalition fighting in Yemen, offering the biggest condemnation to date of a three-year policy linked to tens of thousands of deaths, hundreds of alleged war crimes and bitter stateside debate under two presidents.

Fourteen Republicans voted with every single Democrat in the chamber to consider a resolution authored by Sens. Bernie Sanders (I-Vt.), Chris Murphy (D-Conn.) and Mike Lee (R-Utah) that demands the policy be ended within 30 days. Thirty-seven senators, including Senate Majority Leader Mitch McConnell (R-Ky.), voted the other way, to preserve without debate the status quo of American intelligence, logistical and diplomatic assistance for the Saudi campaign.

The 63-37 vote represented a huge win for lawmakers and outside groups who had been trying to build support for the anti-war effort since the last time a measure was brought up in March. That resolution failed by a vote of 55-44.

Moreover, intense efforts by the Trump administration to defend the policy ― including a closed-door briefing with senators earlier in the day by Secretary of Defense Jim Mattis and Secretary of State Mike Pompeo ― backfired, as powerful GOP senators like Bob Corker of Tennessee, the chair of the Senate Foreign Relations Committee, and Sen. Lindsey Graham (R-S.C.), a top Trump ally, expressed frustration with top officials.

“I changed my mind because I’m pissed,” Graham, who had previously opposed the measure, told reporters after the vote. “The way the administration has handled Saudi has been unacceptable. The briefing didn’t help me today at all.”

Other senators similarly complained about the failure of CIA director Gina Haspel to appear at the briefing to discuss U.S. intelligence about Saudi authorities’ roles in the murder of journalist Jamal Khashoggi.

The Senate will now debate the measure on the floor within the next few weeks, and it is likely to face numerous amendments that could water it down. Even if it is ultimately passed, it will not compel an end to the U.S. support for the effort by the Saudis and their partner the United Arab Emirates.

Still, Wednesday’s vote was a landmark moment for the increasingly tense debates over who controls matters of war and peace for the U.S. and what to do about the decades-old U.S.-Saudi relationship.

The way the administration has handled Saudi has been unacceptable. The briefing didn’t help me today at all. Sen. Lindsey Graham (R-S.C.)

“I’ve been at this for 3 years, and I am blown away by this,” Murphy wrote on Twitter.

Lee said he was “thrilled” by the margin of victory on Wednesday.

“I think that shows people are watching this issue, that they’re concerned,” he told HuffPost. “I think it’s significant that we’re fighting someone else’s war a half a world away, a war that’s never been authorized by the Congress. It’s not just the mere formality of going through the motions of declaring a war, it’s about when you don’t go through that process, the American people never get brought in to the discussion about whether or not to sacrifice in American blood.”

The Utah conservative said he saw the vote as more a victory for the separation of powers, particularly the role of Congress in declaring war, than a hit against President Donald Trump, noting that it was President Barack Obama who initially approved the Yemen policy. His comment reflected how multiple factors drove this coalition of senators together: Some saw this primarily as a constitutional issue, others chiefly a humanitarian one, and for most, it appeared that the combination, added to frustration over the Khashoggi killing, made the vote inevitable.

Outside groups who have been major players in the Capitol Hill fight over what’s become the world’s worst humanitarian disaster applauded the senators’ stand.

“It’s about time,” Kate Kizer of the peace group Win Without War wrote on Twitter. She and other advocates for the bill are hopeful for its future prospects.

Corker hinted that some Republicans could end up not supporting it in future votes, said Kate Gould of the Friends Committee on National Legislation. But new Democratic unity on the issue ― 10 voted against the last iteration of the bill ― and the near-guaranteed support of Lee and ally Sen. Rand Paul (R-Ky.) suggests the legislation enters upcoming procedural battles with at least a simple majority of 51.

“The US public does not want to be complicit in Yemen’s humanitarian crisis any longer,” Scott Paul of Oxfam America said in a statement reacting to the vote. “Today was an important milestone in the fight to end US support for the war in Yemen, and this momentum must continue to save millions of lives that are on the line.”