Mitt Romney's campaign says I'm full of it. I said Romney's tax plan is mathematically impossible: he can't simultaneously keep his pledges to cut tax rates 20 percent and repeal the estate tax and alternative minimum tax; broaden the tax base enough to avoid growing the deficit; and not raise taxes on the middle class. They say they have six independent studies -- six! -- that "have confirmed the soundness of the Governor’s tax plan," and so I should stop whining. Let's take a tour of those studies and see how they measure up.