Garry Wills in NYRB reacts to a post by Harvard law prof Robert Unger saying the Obama must be defeated in order to advance the "progressive agenda". I know that I tweeted this as a "must read", but I must needs say more.
First, this bone-headed idea that we must make things bad enough to bring about "real change" or whatever term of adulation you prefer, is a recipe for suffering and disaster. Radical political movements of both the Right and Left love such pure thinking. It's poison! We may not like our choices, but choosing the worse in order to (hope) get the better later is nuts. It just doesn't work that way, not at least often enough to place bets. A failed Mitt Romney presidency is as likely to take the country to the right as it is the left, and perhaps more so. And the left--well, it's track record, when it comes to radical reform, is poor. Incremental change is often frustrating and difficult to stomach, but radical change is most often for the worse.
Wills wrote an excellent piece in Harpers (alas, gated) about politics in 1976 entitled "Feminists & Other Useful Fanatics" that addresses these same issues. Wills has admiration of the purists, the 'saints", like feminists, Martin Luther King, Jr., and others, but he also understand the role of politicians. The two roles are different, and we really shouldn't try to mix the two very closely or very often. The purity of the saint won't work for the politician, and the compromise inherent in politics sullies the saint (or prophet, as I believe Wills refers to them as well.)
I go with the realists, the incrementalists, the politicians.
(For another great statement of the perspective, go read Max Weber's "Politics as a Vocation", especially the part about the two ethics.)