One of the durable myths of American politics is that Franklin Delano Roosevelt exercised a stroke of brilliance when he appointed the notorious rogue Joseph Kennedy to head the Securities and Exchange Commission, supposedly on a "set a thief to catch a thief" maxim; having been involved in speculation and questionable business practice himself, Kennedy was the perfect person to catch others' chicanery, or so the theory goes. "Wrong," says Prof. Bainbridge. "Kennedy used his position at the SEC to settle old scores from his days on Wall Street, put potential future competitors out of business, and advance the political prospects of friends and family. But, heck, isn't that what the revolving door is for?"