When John Kerry recently admitted that, even knowing what he knows now, he’d still have voted to give the president the authority to invade Iraq, the Bush campaign team was elated. President Bush immediately assailed Kerry as a flip-flopper.

But that’s not quite right: Kerry hasn’t changed his position on Iraq. In October 2002, when the congressional vote was held, Kerry, like most members of Congress, was in favor of punting the question of war or peace to the president and avoiding accountability for the decision. And Kerry remains firmly in favor of avoiding accountability for Iraq today. That tells us something about John Kerry as a candidate. More importantly, it tells us a lot about the health of Congress as a political institution, and about the erosion of Congress’ power to declare war.

As James Madison put it, “In no part of the Constitution is more wisdom to be found, than in the clause which confides the question of war or peace to the legislature, and not to the executive department.” But Kerry, and a majority of senators and House members, ignored that wisdom and voted for a use-of-force resolution that Sen. Robert Byrd (D.-W.Va.) rightly denounced as a “blank check” to the president. The language of that resolution was clear: “The President is authorized to use the Armed Forces of the United States as he determines to be necessary and appropriate in order to (1) defend the national security of the United States against the continuing threat posed by Iraq; and (2) enforce all relevant United Nations Security Council resolutions regarding Iraq.” Thus, Congress left it up to the president (“he determines”) to decide whether and when to initiate the war.

Kerry has since complained about how the president exercised that authority. Bush, he says, violated Congress’ trust by not building a large enough coalition and getting the U.N. on board, “…and that’s why I was upset about it.”

But if Kerry was upset, he has only himself to blame. Complaining about the president using the authority you’ve granted him is rather like locking the barn door after you’ve deliberately let the cows out.

Kerry still hasn’t said whether he was in favor of invading and occupying Iraq. But he’s firmly against botching the job (who isn’t?). Such evasiveness is all too common in Congress. The imperial presidency continues to grow largely because many legislators want to duck their responsibility to decide the question of war and peace; delegate that responsibility to the president; and reserve their right to criticize him, should military action go badly.

Congressional scholar Louis Fisher compares the Iraq vote to the Gulf of Tonkin Resolution that empowered Lyndon Johnson to expand the Vietnam war. As with the Iraq war resolution, the Gulf of Tonkin Resolution was broadly worded to allow the president to make the final decision about war all by himself. Lyndon Johnson compared the resolution to “grandma’s nightshirt” because it “covered everything.” And, as with Iraq, the president did not immediately use the authority granted him. It would be six months later, after Johnson defeated Goldwater in the November election, before the war escalated with a sustained bombing campaign in North Vietnam. In Iraq, President Bush waited five months before launching Operation Iraqi Freedom. As Fisher put it, “In each case [Vietnam and Iraq], instead of acting as the people’s representatives and preserving the republican form of government, [Congress] gave the president unchecked power.” In each case, it was easier to dodge the issue than to take responsibility.

When that kind of cynical calculus reigns, it’s little wonder our representatives want to rush past their most solemn responsibility and get back to spending money to reward favored constituencies. That’s how Senator Kerry and Senator John Edwards, the man who would later become his running mate, both saw it at the time. In the run-up to the vote, Edwards said, “In a short time Congress will have dealt with Iraq and then we’ll be on to other issues.” Kerry echoed: “We will have done our vote.… you’re not going to see anything happen in Iraq until December, January, February, sometime later.… And we will go back to the real issues.”

But the question of war is a “real issue,” if anything is. It’s the gravest issue the Constitution requires Congress to decide. That prominent senators — and presidential candidates — squirm to avoid responsibility for it does not bode well for the future health of either branch.