Romney's claim that Obama would raise taxes on the middle class by $4,000 has earned him three Pinocchios in the past. 

The figure is drawn from a very dry report titled “A Simple Measure of the Distributional Burden of Debt Accumulation.”

The study tries to calculate the burden of servicing the national debt by various income groups, examining what would happen under current law, current policies and Obama’s budget. (Current law refers to policies that are supposed to happen, such as expiring tax cuts; current policy reflects the fact that Congress has said it will not let certain tax cuts expire.)

Among the three scenarios, there’s actually not much difference — for households making between $100,000 to $200,000, the burden would be between $2,800 to $5,400 a year through 2022 — and the Obama administration’s budget falls right in the middle. In other words, the study shows how much lower taxes could be if the nation did not keep adding to the debt load; it does not show, as the ad claims, that Obama has some sort of secret plan to raise taxes.

Presumably, a Romney budget would fall in the same range, but he has not provided detailed plans. “We aren’t really able to run the overall numbers for Romney because we were trying to use the plans for which we had good budget projections,” said Matthew Jensen, one of the co-authors.

 Indeed, the study also looks how the distributional burden rose under George W. Bush — and he of course cut taxes, repeatedly. So just because the debt burden rises, that is not proof that a president will raise taxes.