A strategy of attack and retreat worked out pretty well for Attila the Hun. That might just be what Pelosi and Ried are doing.
I live in Asheville of Western North Carolina. While Asheville is overwhelmingly progressive, the congressional district is overwhelmingly conservative. We just took a seat from a 16 year Republican incumbent and replaced him with a Blue Dog (ex football star Heath Shuler). He is what Speaker Pelosi call a 'majority maker'. His hold on this district is tenuous and has already been targeted by the RNC in '08. Rep. Shuler voted against stem cell both times. While this sucks, it gives him political capital with local conservatives. These are the people we need to win over to end this war.
Also, let's not forget that the Dems DID force a compromise with the liar-in-chief. Bush originally said that he would veto a short term funding bill. The Dems forced a four month bill on him so they can bring it up again after they pummel his popularity some more this summer.
About the Dems popularity - their numbers are down for NOT acting. It plays perfectly to the mainstream media. Let the media beat them up for not being tough. That gives them a stronger mandate to get tough.
While it is hard to stomach the price that our soldiers and their families will pay this summer, how irresponsible would it be for the Dems to make a foolish tactical move that might cost them all if their political capital to end this war. As grim as this is, smart generals make these decisions all the time. We need smart generals.
...or they might just be wimping out. We'll find out in September.