It is difficult to overstate the extent to which political speech in America today is shaped—in volume, timing, and style—by federal election laws and Federal Election Commission regulations. When political actors and issue groups seek to disseminate a message, their first call is often to a lawyer: “How should I organize? Who may contribute to my cause? What am I, and other people and groups that support me, allowed to say?” In recent months, several groundbreaking decisions have shifted dramatically the boundaries of permissible conduct, raising such questions to a fever pitch...