The Democrats have different factions, you have the progressives (similar to social-democrats in europe, but obviously working within the American situation), the Blue Dogs (corporatists, that think gay marriage and abortion is ok), and the New Democrats (Obama centrists, basically corporatists that still want to pretend to be progressive).
The Blue dogs are a dying breed imo, now you have the new democrats, clintonites, obama democrats, who want to be your typical pro-buisiness liberal and who don'y really have any progressive principles, and the progreessives, who want to be old school progressive liberals.
I believe thay many progressives are actualy working for the benefit of hte working class, the problem is, their progressive policies will ALWAYS be shot down, by the new democrats and the republicans. The New democrats will always temper the progressives and bring them as right as possible, and then after that, they'll negotiate with the republicans to bring it even more right.
The healthcare debate was a case in point example of this.