They lie as a matter of course

Princeton Economist: Obama Campaign Is Misrepresenting My Study on Romney's Tax Plan

John McCormack

Last night, the Obama campaign blasted out another email claiming that Mitt Romney's tax plan would either require raising taxes on the middle class or blowing a hole in the deficit. "Even the studies that Romney has cited to claim his plan adds up still show he would need to raise middle-class taxes," said the Obama campaign press release. "In fact, Harvard economist Martin Feldstein and Princeton economist Harvey Rosen both concede that paying for Romney’s tax cuts would require large tax increases on families making between $100,000 and $200,000."
But that's not true. Princeton professor Harvey Rosen tells THE WEEKLY STANDARD in an email that the Obama campaign is misrepresenting his paper on Romney's tax plan:

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. 

You can check the math that shows Romney's plan is mathematically possible here.