Ace nails it, the pledge was always a LIE.
Obama's "pledge" was always a lie, and the media repeated his promise incessantly, and uncritically, to sell Obama as a different kind of Democrat. They never inquired how it was he could spend so much more without bankrupting the country if he also did not raise taxes on the middle class -- a bit of easy math would have shown this as an impossibility, but, alas, the media was apparently told there would be no math in this election.
Obama originally planned -- and stated as much -- to tax the middle class by levying huge carbon taxes which would of course hit the middle class (and poor, for that matter). He confessed -- or rather proudly declared -- that his planned carbon taxes would "necessarily" cause electricity rates to "skyrocket" -- and again, the media simply ignored this, and again, simply insisted to the public that Obama's word was bond about not raising taxes. Even though he just announced that taxes would be raised in the form of "skyrocketing" electricity costs.
That was Obama's Plan A for raising taxes on the middle class -- taxing the living hell out of the motive force of our economy, energy, which every single human being and business uses in varying quantities.
His Plan B was the VAT.