Obama's $5 trillion tax cut claim against Romney is a fiction

Robert Samuelson has his usual nice, even handed discussion here:

Here's Obama at one rally:"My opponent, he believes in top-down economics, thinks that if you spend another $5 trillion on a tax cut skewed towards the wealthy that prosperity will rain down on everyone else."
It's a powerful argument, marred only by the fact that the $5 trillion tax cut is a fiction. . . .
To justify its $5 trillion figure -- the estimated tax loss over a decade -- the Obama campaign had to cherry-pick Romney's proposal and the TPC analysis. It had to ignore any revenue raised by reducing tax breaks and assume that, faced with a conflict between the rich and the middle class, Romney would automatically side with the rich -- as opposed to shielding the middle class from any tax increase. On Wednesday, Romney promised to protect the middle class.
The TPC report was widely interpreted as saying Romney would have to raise taxes on the middle class. It didn't, says the TPC's Howard Gleckman. It simply pointed out that he couldn't keep all "his ambitious campaign promises." He'd have to make choices and modifications. So what else is new? . . .