Senators are ready to pack their bags and head out of town before the hot, swampy weather in Washington gets any more unbearable. But of course, not before they humiliate themselves and let down their constituents one last time — by voting down an amendment that would have prevented an unauthorized and unconstitutional war with Iran, as they did on Friday.

The bipartisan amendment, sponsored by Sens. Tom Udall, Tim Kaine, Rand Paul, and Mike Lee, was short, sweet, and appropriate at a time when the U.S. and Iran seem minutes away from a direct conflict. The language was as clear as day: “no funds authorized by this Act may be used to conduct hostilities against the Government of Iran, against the Armed Forces of Iran, or in the territory of Iran.”

Under this amendment, if President Trump (or any future president) thought military action was a necessity to defend the interests of the United States, he would first need to do what the Constitution clearly requires: make his case to Congress and attain authorization from our elected representatives. Lest there was any worry about the amendment tying the president’s hands in extraordinary circumstances, it allowed Trump to respond militarily if U.S. forces were attacked.

Republican senators such as Majority Leader Mitch McConnell, Armed Services Committee Chairman James Inhofe, and Marco Rubio argued before the vote that the amendment was dangerous, unnecessary, and counterproductive. Sen. Tom Cotton, R-Ark., who would have probably invaded Iran already if he were sitting in the Oval Office, made the ludicrous claim that reaffirming Congress’ war powers “embodies irresolution & weakness.”

But if there is any weakness here, it’s on the shoulders of those who voted down the measure and are apparently perfectly fine with bestowing the president with monarchical war powers. George Washington, John Adams, James Madison, and the rest of the founding fathers obviously felt much differently, understanding that taking a country to war is a decision far too important for one man to make.

And there was nothing in the Udall-Kaine amendment that was unconstitutional or unreasonable. Indeed, the language was in keeping with what Article I, Section 8 of the U.S. Constitution already states in black-and-white — that it is the legislative branch, not the executive, that determines when the country goes to war. And of course if the U.S. is attacked, the president reserves the right to strike back in self-defense without first coming to Congress.

Paradoxically, what the Senate did today was vote against the declare war clause, the most important provision in the country’s most important document. While the executive branch finds ever more clever ways to expand its power, senators chose to negate their own rather than fight to preserve it. And for that, they should be ashamed.

Daniel DePetris (@DanDePetris) is a contributor to the Washington Examiner's Beltway Confidential blog. His opinions are his own.