The Left has no sense of what its own political success, if achieved, would mean; it has no articulated vision of a good, or even of a better, society. In the absence of such a vision, to be on the left is simply to be in a state of permanent protest. And since the thing most protested against is the damage wrought by rapid change, to be on the left is to be a conservative.-- Tony Judt, "The Social Question Redivivus," in Reappraisals, p. 427.
... Judt's particularly discussing the European left, but I recognize the application to America as well. Compare this Crooked Timber post.
... Interview with Judt here. Ill Fares the Land is a short hardcover with few words per page, which for its ostensible purpose ought to've been published as a paperback original; but then, Judt probably needs the money, poor guy.