Democrats have been working to thwart President Donald Trump’s military campaign aimed at preventing Iran from acquiring nuclear weapons since the initial strikes began. However, they were unable to advance a measure that would have ended the hostilities, even as four Senate Republicans crossed party lines to vote with Democrats.

Centrist Senator John Fetterman (D-PA) took a decisive role in securing a 47-46 victory for Trump’s policy by voting against the motion. The motion, sponsored by Democratic Senator Raphael Warnock (D-Ga.), sought to discharge a war powers resolution from the Senate Foreign Relations Committee.

The motion to discharge failed 47-48 as Fetterman voted with Republicans to block it. Five senators did not vote: Senators Michael Bennet (D-Colo.), Cory Booker (D-N.J.), Josh Hawley (R-Mo.), Mitch McConnell (R-Ky.), and Bernie Sanders (I-Vt.).

The four Republican senators—Rand Paul (R-Ky.), Susan Collins (R-Maine), Lisa Murkowski (R-Alaska), and Bill Cassidy (R-La.)—had previously supported a similar motion to discharge a war powers resolution sponsored by Senator Tim Kaine (D-Va.) last month, which passed 50-47.

Maverick Senator Thom Tillis (R-N.C.) indicated before the vote that he was considering joining the four Republicans in voting yes.

The vote occurred as U.S. and Iran look ahead to formalizing an agreement to end hostilities.

The war powers resolution, led by Senator Raphael Warnock of Georgia, would direct 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.”

Speaking on the Senate floor ahead of the vote, Warnock appealed to his colleagues: “After 109 days of a failed war, and now a fragile, temporary, but welcome truce, will my Republican colleagues choose today to finally stand up to this president?”

Recent weeks have seen cracks in GOP support for the war. Last month, the Senate advanced its first resolution to limit President Trump’s war powers in Iran after seven failed attempts. Senators approved the motion to discharge the resolution from committee 50-47, with the same four Republicans supporting Warnock’s resolution on Tuesday. Three GOP members were absent during that vote, tipping the scales in Democrats’ favor for the first time since the Iran conflict began.