It is not the same situation. The Gulf War was fought because an one of our allies, Kuwait, was attacked and overrun. As for why Kerry did or did not vote against it, I can't say. I would disagree with him in that instance. I would also agree that granting the power to the president to act is appropriate. The assumption is that the president is going to responsibly act and not commit troops into a violent situation without absolute proof of impending danger. He did not do that. The "proof" was unverified and now over a thousand troops are dead and thousands more are maimed and injured.