I can’t tell exactly how the Obama campaign reached that characterization of my work. It might be that they assume that Governor Romney wants to keep the taxes from the Affordable Care Act in place, despite the fact that the Governor has called for its complete repeal. The main conclusion of my study is that under plausible assumptions, a proposal along the lines suggested by Governor Romney can both be revenue neutral and keep the net tax burden on taxpayers with incomes above $200,000 about the same. That is, an increase in the tax burden on lower and middle income individuals is not required in order to make the overall plan revenue neutral.
Romney provides details on his tax plan on his website.
John McCormack explains how the math works at the Weekly Standard.