The Senate voted on Tuesday to advance a war powers resolution aimed at forcing Donald Trump to end the war in Iran unless he receives congressional authorization to continue it.

Tuesday’s 50-47 vote marks the first time the chamber has advanced the bill, the eighth attempt at doing so since the conflict began in February.

Four Republicans joined all but one of the Senate’s Democrats in voting to pass the bill.

This time, Senator Bill Cassidy, fresh from a primary loss in Louisiana in a race where Trump endorsed his opponent, voted to take up the measure.

“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 wrote on social media after the vote. “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.”

Lisa Murkowski of Alaska, Rand Paul of Kentucky and Susan Collins of Maine also voted to advance the bill, as they did in previous votes. John Fetterman of Pennsylvania was the sole Democrat to vote against it, while three Republicans did not vote.