"This is a constitutionally significant moment," said Tim Kaine, Democratic senator from Virginia and the resolution's lead sponsor. "Congress is finally reclaiming its constitutional role in decisions of war and peace."

The shift reflects growing unease among some Republicans about the administration's escalating rhetoric toward Iran. At a press conference last week, Trump declined to rule out preemptive military strikes against Iranian nuclear facilities, a statement that reportedly alarmed Senate GOP leadership.

Collins, in a statement explaining her vote, pointed to the administration's lack of consultation with Congress. "The executive branch has not provided adequate briefings on military planning or diplomatic alternatives," she said. "That's unacceptable when we're discussing potential military action."

The resolution now faces additional procedural votes before a final passage vote, where it would need 60 votes to overcome a likely filibuster. Even if it passes the Senate, it faces an uncertain future in the House, where the Republican majority has shown little appetite for limiting presidential war powers.

And even if both chambers passed the resolution, Trump would almost certainly veto it, requiring a two-thirds supermajority in both chambers to override—a threshold that appears mathematically impossible given current party alignments.

Still, the advancement of the resolution sends a political signal that could influence administration decision-making. Previous presidents have scaled back military plans when faced with congressional pushback, even from non-binding resolutions.

"This puts the administration on notice," said Jack Reed, Democratic senator from Rhode Island and chairman of the Armed Services Committee. "Any strike on Iran without congressional authorization will face serious political consequences."

The Trump administration has argued that the president has inherent constitutional authority to defend American interests without congressional approval, particularly in response to threats against U.S. forces or allies. The White House issued a statement calling the resolution "dangerous" and "an unconstitutional infringement on executive authority."

But legal scholars note that the War Powers Resolution of 1973 explicitly requires congressional authorization for sustained military operations, except in cases of imminent threats to U.S. territory or forces. Courts have historically avoided ruling on war powers disputes, leaving the issue as a political rather than legal question.

The Republican defections also highlight broader tensions within the GOP about Trump's foreign policy approach. While the party largely supports a tough stance on Iran, some senators have expressed concerns about the lack of diplomatic engagement and the potential for military escalation without clear strategic objectives.

"I support pressure on Iran, but I want to know the endgame," said Romney, who has frequently clashed with Trump on foreign policy. "We've seen what happens when America enters conflicts without clear plans for achieving our objectives."

As Americans like to say, 'all politics is local'—even in the nation's capital. And for senators from both parties, the prospect of another Middle East conflict resonates with constituents weary of two decades of war in the region.

The resolution faces additional votes this week, with final passage possible by Friday. Even symbolic victories in Congress can shift political calculations, and the administration will be watching to see if Republican defections expand as the vote moves forward.

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