Herman Cain's supporters know their part by heart. On the campaign trail, at the point in Cain's stump speech when he begins to discuss his plan for economic growth, they're always ready to join the chorus: "Nine! Nine! Nine!" They're referring, of course, to the Republican presidential candidate's proposal to throw out today's tax structure and replace it with a 9 percent income tax, a 9 percent business tax, and a 9 percent national sales tax. Cain would eliminate capital gains taxes, the payroll tax and the estate tax. For Cain, a Georgia businessman, 9-9-9 is a perfect platform. It's...