Jerry: Whether passing a prescription-drug benefit was a “defensive” move designed to protect the then-existing Republican majority or an “offensive” move designed to expand it is beside the point. (As it happens, though, your correspondent is wrong about what was “well understood” at the time by Republican players, and I have the interview notes to prove it.) Given the extremely strong public support for a drug benefit — something you still aren’t addressing — it is hard to believe either that Bush would have won the election in 2000 without promising a prescription-drug benefit or that he would have been re-elected without delivering on that promise. The issue was surely powerful enough to tip Florida in 2000 and Ohio in 2004. Bush made some efforts to steer the bill in a direction that most conservatives would consider more “responsible,” but these were shot down on the Hill. (I’d be happy to concede that he could have done more.)
Senator DeMint’s comment is an assertion with no evidence to back it. He offers no reasons for doubting the foregoing analysis of 2000 and 2004. Nor is it at all credible that the bill destroyed GOP credibility on spending and entitlements and thus paved the way for the defeats of 2006 and 2008. If this were true, we would have expected GOP support to fall more deeply among conservatives than moderates, and we would expect it to fall in 2004 (right after the bill was passed) rather than in 2006 (when Republicans were more tightfisted). The actual pattern of results was exactly the opposite: Republican support fell more deeply among moderates and did so long after the drug benefit passed.
Bottom line: You’ve presented no reason to doubt that the real-world alternative to the prescription-drug bill was likely to be a more expensive version of the same.