That is simple - there is no alternative, no other party capable of winning elections in this vast corporate wasteland. It is either Dems or nothing for the progressives. Do not blame Dems for that. Blame the US electoral system and the American sheeple with their religion- and 'Murica- infested pea brains who keep elected the pro-business right wing trogs that keep the status quo intact. Unlike, say, the x-USSR where nobody asked for popular opinion, in the US the reactionary trogs that run this country have been freely elected and enjoy genuine support of the majority of the voters - who also consistently reject progressive candidates of any shape and flavor from Kerry to Nader, to Dean and to Kucinich. Why do you think progressive candidates do not even make it to the primaries, let alone winning any elected offices?
It has always been like that - consistent popular support for right-leaning politicians with the single exception of the Great Depression era when the sheeple got a good kick in the teeth and wanted a knight on a white horse to come and save them. They just got lucky that the knight they got was on a wheel chair and had some forward thinking ideas in his head, rather than being a downright fascist.
So again - do not blame Democrats, blame the system and the people who freely support it. To be sure, I am as disgusted with Dem politics as you are - however, I do not blame the messenger for the message whose contents suck.
Wojtek