The reason Paul Wolfowitz should resign as president of the World Bank has nothing to do with Iraq, or his last job as No. 2 in Donald Rumsfeld’s Pentagon, or even his clashes with the bank’s directors and staff. He should resign because he made clean governance his main cause at the bank and has fallen far short of his own standards. The facts are not in dispute. When Mr. Wolfowitz was appointed he was in a personal relationship with a woman employed there. Since working under Mr. Wolfowitz’s supervision would violate the bank’s conflict-of-interest rules, she was reassigned to...