The bipartisan Tax Policy Center reports what serious economists seem to have been saying, Romney's tax plan does not add up. Ronmey's saying it adds up does not make it so.
Useful reading from the New York Times: Romney's tax plan
And here is TPC's original report: The TPC report

Barack, didn't you watch Bill?

One would think Obama would have taken advantage of Bill Clinton's bravura speech at the DNC as a guide for promoting his own candidacy. But no. So where go the mojo? Alas, no pinch hitters in presidential debates.

David Firestone's piece in the NYT characterizes last Wednesday night as a debate without substance. No, The Debate Was Not Substantive Seems to me there was substance. However the substance comprised mostly untruths (e.g. $716 billion Medicare cut) or total amnesia (I never promoted a $5 trillion tax cut). Didn't Romney know there's footage! The fact checkers have exposed a number of Romney's doozies (read: untruths) although the recants don't make headlines like those of his debate "victory". Debate lesson: You can blaze away with made up data because people will remeber the false claim not the retraction.
Presidential Debate Fact Check
Romney's Impossible Tax Promise