Yes, that 5% could have been swayed if the Republicans (and more specifically McCain) had balked at the size and scope and implementation of the “bailout”.
But after the House GOP rejected a 50 page bill, the Senate made a 450 page monstrosity that bought their support (showing that our guys are for sale, and they are expensive, and the payment comes out of our taxes).
McCain was just the kind of guy that this “bipartisan” bill would attract, but if he wasn’t, or he made a calculated political move and rejected the bailout, he could have easily swayed that 2.6% he needed, or gotten more actual conservatives to the polls.