A reader letter at TPM makes some good points:
Instead [many progressives] feel like the people they voted for and trusted to lead them failed. And it's hard to imagine making that same emotional commitment again in the future. Self defeating, yes. Temporary, maybe. But we're talking primal stuff here - people don't like wimps, not matter what party.Two points deserve some elaboration: emotional investment, and wimps.
Leaving aside whether they should or not, it's clear that progressives work off of emotion a lot of the time. That is not surprising, because it takes a certain amount of courage to publicly advocate for a substantial change in society. Doing so means potentially facing disapproval from the rest of society, facing the fear of proposing a something new and untested, and facing the fear of failure. Nobody would choose to go up against those obstacles without a good reason and some passion. So progressives have to work themselves up before heading out to organize and campaign. And because of the nature of the emotion, progressive's energy can be deflated fairly easily. Contrast this with the other side, which has a default position against change, and frequently operates on hate or fear. The latter two emotions are much more enduring than hope.
The epitaph of "wimp" is something that has been lobed at Democratic politicians for a while. Sometimes the accusations stem from the fact that Dems are such a broad coalition it's hard for them consistently agree to anything. It's so broad there is a large group within the nominal coalition that regularly campaigns against the national party. Sometimes the accusations result from the asymmetry of effort between not doing anything and doing something (see above), meaning Democrats can potentially concede far more territory than Republicans. And sometimes liberals really are too open-minded.
This time around the accusation stems from the impression that no Democratic leader appears to have worked hard for a good bill (except Ted Kennedy until he got too sick). AFAICT, the administration didn't put its muscle behind a progressive version of the bill. Reid seemed perfectly happy to let Baucus drag out the "negotiations" in the secretive Terrorist Cell of Six. He also rejected using the budget reconciliation process as an option, meaning every Democrat could exploit the supermajority rule. And finally, the Senate leadership repeatedly and very publicly caved to Lieberman and Nelson every time they came up with a new objection. Nobody has even hinted about disciplining either.
It's always fun to speculate about motivations, but they're beside the point. The clear message from the process, combined with disappointments on other issues, is that Obama is not fighting for progressive values. Nor is the Senate leadership. Whether progressives have reasonable justifications for expecting a good effort is beside the point as well. They have expectations that are not being met, and their hope is deflating. And that will have consequences.