We have long assumed that the infestation of special interest money in Washington is at the root of so much that ails our politics. But what if we’ve had it wrong? What if instead of being bribed by wealthy interests, politicians are engaged in a form of legal extortion designed to extract campaign contributions? Consider this: of the thousands of bills introduced in Congress each year, only roughly 5 percent become law. Why do legislators bother proposing so many bills? What if many of those bills are written not to be passed but to pressure people into forking over cash?...