Ed Kilgore asks liberals to think a couple moves ahead:

[P]ersonally, I consider ever-worsening economic inequality the great undiscussed issue of our time, and think the abolition of estate taxes would be morally obscene. But those who urge a course of action that makes these positions non-negotiable have a responsibility to game-plan this out a bit in terms of real-life consequences. "Fighting" is not a strategy; nor is "drawing a line in the sand." No rebellion is going to change the Obama administration's handling of the 2009 stimulus bill or the 2010 health reform bill. And you can't make the tax issue a no-brainer: yes, Obama did promise to oppose extension of tax cuts keyed to the top bracket, but he also promised, much more vocally, to extend the rest of them, so he's going to have to break a promise anyway you look at it.