One big problem is the way information is presented in elections (and the depth at which voters analyze things). If Congressman X votes for this package as written, his opponent's campaign ads practically write themselves:
(Start threatening music, go to unflattering B&W photos, begin authoritative baritone script- "Congressman X voted to SLASH Medicare and Medicaid . . .but held out for a cut in the tax rate for his friends in big corporations. He cut funding for national defense as we are engaged in two wars. He even wanted to increase the taxes paid by injured veterans . . .") The big picture hardly matters, the nuances of the entire package, etc. Few will listen to Congressman X's rationale, it will be drowned out in the deluge of negative ads.
One nice thing about a big, fairly high profile package like this one--voters can read it, see all the tradeoffs in context, and get comfortable with a "yes" vote by Congressman X ("Yep, I remember there was plenty in there I didn;t like, But Congressman X probbaly voted for it for the same reason I would have--it was better than what we were fixin to do, which was nuthin."). But folks have to take the time to read it.