What is wrong with asking Congress for authorization to go to war?

What, indeed, is wrong with asking Congress for authorization to go to war? The power of the imperial presidency and the irrelevance of the Constitution has been so much taken for granted that most politicians and pundits have been thrown into a state of shock and confusion over this unexpected turn and have manifest difficulty in answering the question. The most popular objection seems to be that it shows weakness of US leadership. This follows from the Louis XIV theory of leadership, ("L'etat, c'est moi"), that the president is the state -- nevermind that Congress allowing itself to be shut out of its constitutional duty would certainly be weakness by any reasonable measure. If Congress is counted as a co-equal branch of government, as it properly should be, then US leadership has been weak for many years. Congress has, in particular, been Israel's shameless poodle in all matters relating to the Middle East. It would be wonderful, however unexpected, if Congress would take this occasion to play a leadership role on behalf of the American people for a change.