The Senate voted 55-45 on Thursday in favor of a war powers resolution curbing President Trump's ability to launch military action against Iran without congressional authorization.

Why it matters: It's a bipartisan rebuke of the president's foreign policy that passed even after the White House threatened to veto the resolution.

Eight Republican senators — Mike Lee (R-Utah), Lamar Alexander (R-Tenn.), Bill Cassidy (R-La.), Jerry Moran (R-Kan.), Lisa Murkowski (R-Alaska), Todd Young (R-Ind.), Rand Paul (R-Ky.) and Susan Collins (R-Maine) — joined Democrats in voting for the resolution.

Between the lines: The House last month passed a "concurrent" war powers resolution, which does not have the force of law or go to the president's desk for a signature. "This is a statement of the Congress of the United States," Speaker Nancy Pelosi said at the time. "I will not have that statement diminished by having the president veto it or not."

The Senate measure is a more forceful "joint" resolution, meaning it can be voted on by the House and sent to Trump's desk to be enacted into law. The Senate does not have the two-thirds majority necessary to override Trump's veto.

What they're saying: Lee, who ripped into the Trump administration last month for its handling of the classified briefing on the killing of Iranian Gen. Qasem Soleimani, said, "For me, this is about supporting President Trump in his foreign policy, in his effort to make sure that we don't get involved too easily, too quickly, in an unconstitutional way, in any war."

Senate Minority Leader Chuck Schumer (D-N.Y.) acknowledged that Trump would likely veto the resolution, but said: "It sends a shot across his bow that the majority of the Senate and the majority of the House do not want the president waging war without congressional approval."

Trump tweeted Wednesday: "It is very important for our Country’s SECURITY that the United States Senate not vote for the Iran War Powers Resolution. We are doing very well with Iran and this is not the time to show weakness."

What's next: Speaker Nancy Pelosi said in a statement that the House will take up the Senate's joint resolution "in the coming weeks."

The big picture: This is not the first time bipartisan senators have joined forces to rebuke Trump's Middle East policies. The Senate has passed resolutions calling on Trump to pull U.S. support from the Saudi-led coalition in the war in Yemen and blocking the administration's sale of arms to Saudi Arabia. Both were vetoed by Trump.

Go deeper: White House threatens to veto Iran war powers resolution