After reading this Boston Globe article about your Iraq vote, I started to wonder why you give those slimy bastards on the right more rope with which to hang you. I know you want to take an honorable stance and not let on that the current president of the USA can't be trusted to take the country around the block, much less to Iraq. But it's time to call a duck, a duck. I've come to agree with an alternative answer that a certain professor I know suggested you use the next time the question comes up:
If I had known then that the president and his advisors were going to handle the Iraq situation in such a boneheaded, hamhanded, incompetent way, then I wouldn't have voted to give the president authorization to go to war. I made my vote on the assumption that the president could be trusted to act responsibly. Obviously, I was mistaken.
It's short but sweet.