Although I agree with Phil that President McCain might not have been any worse than Bush, I'm not entirely sure we would have dodged the Medicare prescription drug benefit bullet. Bush's advocacy of that entitlement expansion didn't come in a political vacuum. It is much easier to be one of ten senators bucking a popular trend than a sitting president, especially given that neither Bush nor McCain are known for their deep-seated opposition to activist government (though McCain is better on issues related to government waste).
Of course, even if we had gotten a more limited, means-tested prescription drug benefit with some of the market-based incentives factored in, we would have been better off than we are now.