I'm sure they're sincere; that's my objection: The pledge is no more than political cover from the general electorate and colleagues on the other side for an intractable position to which they'd already committed.

As for accepting tax hikes only accompanied by cuts several times larger, that's the "grand bargain" Obama offered, the one with $3 trillion in cuts for just over half a trillion more in taxes that would've saved our credit rating, so we're back to what he told Cantor: Talk to your Speaker; even if we ignore the "spending cuts" for planned military withdrawals that was a roughly 4:1 ratio of spending cuts to taxes, so what more do you want? Even working on the dubious assumption that Democrats are any less servants of corporate interests than Republicans are, there's nowhere near enough trust for either side to expect the other to give make a major concession later if they make one now. It has to be simultaneous by both sides, because that's the only way to ensure neither reneges once they get what they wanted; Joe Lieberman proved that two years ago.

As for whether taxing the rich will help rather than hurt or the need for far greater spending cuts, we're running out of things to cut and have the lowest taxes of the past half century, so I obviously disagree.

EDIT: For greater precision.