Martin Feldstein posits that Romney's plan won't necessitate middle-class tax cuts:
Since broadening the tax base would produce enough revenue to pay for cutting everyone's tax rates, it is clear that the proposed Romney cuts wouldn't require any middle-class tax increase, nor would they produce a net windfall for high-income taxpayers. The Tax Policy Center and others are wrong to claim otherwise.
Several experts at the Tax Policy Center conducted an exhaustive re-run of Feldstein's math – and came up way short:
[T]he net effect would be cutting taxes on households above $200,000 and thus requiring net tax increases on households with less income. More broadly, both our analysis and Feldstein’s show that Romney’s tax plan cannot accomplish all of his stated goals. Either taxes must rise on those with income below $200,000, or tax preferences for saving and investment will have to be reduced, or revenues will be cut, or promised tax cuts for high-income households will have to be reduced. Trade-offs exist and solutions are possible, but tax reform cannot do everything that it is sometimes asked to do.
But that's not even the point, they add:
[T]he debate over what is or isn’t possible distracts from the more important question of what the Romney plan actually is. The governor could settle this issue quickly simply by describing how he’d pay for his tax cuts.