How about among independents, a key group that Obama is struggling to hold onto. This is the group that looks for bi-partisanship more than Republicans or Democrats. If the Democrats spit in the face of Republicans and thumb their nose at bi-partisanship and "go it alone", to borrow a phrase from the Bush years, will that destroy Obama's image of trying to reach across the aisle that he campaigned on. Will that hurt the Democrats or affect the make-up of the Congress in anyway on November 2, 2010?
I think voters will have long enough memories to recall that most Republicans balked at passing ANY sort of health care reform and, with a few exceptions, did not reciprocate good faith efforts at bipartisanship. Yes, Democrats will probably end up "going alone" but voters will realize it was because of Republican stubbornness, not Democratic partisanship.