In a bipartisan rebuke of President Trump on Thursday, a Senate majority voted 55 to 45 to block the president from taking further military action against Iran — unless first authorized by Congress. Eight GOP senators joined every Democrat to protest the president’s decision to kill a top Iranian commander without complying with the War Powers Resolution of 1973.

The Democratic House will no doubt agree to the Senate’s resolution and send it up to the White House. But President Trump has already promised a veto, and supporters of the resolution lack the two-thirds vote in both chambers required to override.

Here are three takeaways from today’s Senate vote.

1. Trump is the only president who has been rebuked through the War Powers Act

This is only the third time ever that the full Senate has used its authority under the 1973 War Powers Resolution to block a president from using military force abroad. All three efforts were against Trump — with a Republican-led Senate.

The first such vote came in late 2018 when the GOP-led Senate ordered an end to U.S. military operations abroad in Saudi Arabia’s war in Yemen. The second took place last year, when both the Democratic House and Republican Senate agreed to a measure — vetoed by the president — to curtail U.S. military involvement in Yemen.

Such votes are rare in part because, for the past two decades, presidents have relied on the 2001 Authorization for Use of Military Force (AUMF), which Congress passed after the Sept. 11, 2001, terrorist attacks. But nearly 20 years later, presidents increasingly must resort to contorted interpretations of the law to argue that it covers new conflicts. That may be leading lawmakers to turn to the War Powers Act, because they are reluctant to rewrite the AUMF.

Will Congress’s newfound use of the War Powers Act last, or are lawmakers turning to it because they’re uniquely frustrated with Trump? Surely, one reason for yesterday’s measure was the fact that the president hadn’t consulted with key legislative leaders before launching the drone strike that killed Iranian Maj. Gen. Qasem Soleimani, as the law requires. Similarly, his refusal to break with Saudi Arabia — despite both the humanitarian crisis in Yemen and the killing of Washington Post columnist Jamal Khashoggi — moved both chambers last year to invoke the War Powers Act. What’s more, Congress has taken other steps to rebuke the president over his foreign policy decisions, as when the Senate voted 68 to 23 last year to condemn Trump’s decision to pull military forces from Afghanistan and Syria.

We can’t know whether Congress will attempt to sanction the next president over his or her use of military force abroad. But Capitol Hill’s newfound fondness for the War Powers Act — even when the president’s party controls one or both chambers — is remarkable.

2. Symbolic votes matter

Like Congress’s earlier efforts to reassert its war powers, this measure will not become law. But symbolic votes can matter.

First, the public is more likely to notice conflict in Washington when the elite consensus breaks down. Dissent further undermines a beleaguered White House and reveals some Republicans’ extreme frustration with the president’s justifications for the strike.

Second, congressional signals like these — even when they fail — can shape future foreign policy by increasing the political costs to the president if he or she stays the course. That hardly means these congressional slaps will chasten the president. But they signal presidential weakness.

3. Don’t miss the GOP fractures

Eight Republicans voted against Trump on the Iran resolution, up from seven votes to rebuke the president in 2018 over the war in Yemen. Notably, five senators voted for both the Yemen and Iran war powers measures, joined by three additional GOP senators this time around. The defections came from two wings of the party: Sens. Rand Paul (R-Ky.) and Mike Lee (R-Utah), and middle-of-the-roaders such as Lisa Murkowski (R-Alaska) and Lamar Alexander (R-Tenn.).

These are hairline stress fractures, not a big break in the Senate Republican conference. But any dissent within the president’s party over foreign and military policy is unusual during an era of such heightened polarization and intense partisanship. And it’s especially remarkable while the president has been firing, threatening and otherwise attacking anyone he views as insufficiently loyal now that he’s been acquitted by the House of impeachment charges.