His basic claim is that the progressive wing of the Democratic Party sucks at politics. They suck at politics because they are incapable of making a credible threat to vote against the tiniest incremental improvement on some issue where they would like to see major reform. Their mantra is, "Do not let the perfect be the enemy of the good," but the effect is that the "better than nothing" becomes the enemy of the good. The HCR debate has guaranteed that the Obama administration will never make any major moves to placate progressives within the party because they know full well that the progressives will always back them no matter what. The progressives have destroyed any leverage they might have had with the administration because they have proven themselves unwilling to sink the health care bill, even though it lacks any of their "must have" provisions.
First of all, I think this analysis is spot on.
Second, I think it can be generalized to cover much of the dynamic that obtains between (relatively) liberal and (relatively) conservative blocs in most major political debates in North America. In short, liberals suck at politics because they aren't willing to accelerate the contradictions. The notion that things might have to get worse in order to get better, and that a responsible effort to make things better therefore has to accept making things worse as a valid strategy -- this is beyond the pale of most liberal thought.
If the anti-war "left" had decided to make life really hard for Bush, they could have. Obstructionism is obviously not an entirely lost art in US Congress, and those opponents of the war who had the misfortune of not being elected members of the legislature could have been infinitely more extremist in the expression of their opposition to the war than they were. But that would have entailed making life worse for people other than Bush as well -- soldiers, one's fellow citizens, one's family, etc. It would have meant taking on board the responsibility for causing deaths, even. Being anti-war could not be passed off on one's conscience as being anti-killing, or anti-suffering, or the like. It would mean taking a decision against a concrete policy or act, rather than against only abstract generalities. (If you've decided to oppose this war, then nothing prohibits you from making war against those who would take us into this war, but if you have "decided" to oppose War, there is very little you can do to stop any actual war, which will always be a concrete course of action, carried out by people with guns.)
This unwillingness to make things worse in order to get what you have decided upon as your goal means the progressive left will always get steamrolled by those who are willing to say "Give me what I want or I'll destroy something both of us care about."