The U.S. Supreme Court's 2010 decision in Citizens United v. Federal Election Commission made it legal for corporations and labor unions to spend unlimited sums from their treasuries to influence elections. Follow-up rulings by a federal court and the Federal Election Commission permitted third-party groups to accept unlimited contributions to pay for electioneering expenditures.The five justices who signed the Citizens United ruling based their decision on a view that political spending by outside entities does not pose a sufficient risk of causing corruption to warrant being restricted. Events soon showed that the court's confidence was misplaced.Shortly after the decision, third-party electioneering entities began springing up. These cam...