It was a mistake. On the information we had, we shouldn't have prosecuted the war. We shouldn't have changed our argument from international law to regime change in a non-transparent way. It was an error for which we as a country paid a heavy price, and for which many people paid with their lives.
All of the great leaders have had one characteristic in common: it was the willingness to confront unequivocally the major anxiety of their people in their time. This, and not much else, is the essence of leadership.