Josh Barro goes through all the "studies" Paul Ryan claimed backed up his mathematically-impossible budget tricks, and pokes holes in all of them. Let us now say what it emphatically true: The Romney-Ryan plan for the deficit does not pass basic arithmetic.
Of course, we have no idea what Romney would do in office, except what is expedient for him at any moment. But we do know that the plan as outlined in generalities cannot withstand specific scrutiny. I think that matters. I think we have to ask and ask and ask again for specific tax deductions Romney and Ryan would end to make up for the gaping hole their tax cuts on top of the bankrupting Bush tax cuts would add to the debt.
I don't think Obama can ask that question enough. And one more plea: could Obama at some point simply ask Romney where his policies – foreign and domestic – differ from George W. Bush's and Dick Cheney's? What's different this time? Because a big tax cut we can't afford and a new credit-card war on the basis of non-existent WMDs does not seem like much of a change to me.