An excellent point here from Ezra Klein inspired by Greg Anrig's The Conservatives Have No Clothes which was excellent even when I read it several months ago before it had a pretty cover or nice paper: It doesn't mean anything to suggest that there's a "real" conservatism which exists in the Platonic heavens and is different from the agenda that conservative politicians in fact pursue.
One shouldn't just identify "conservatism" with "the policies pursued by George W. Bush" because in some instances (immigration most notably, but the insertion of greater federal control over schools to some extent and probably on some other things) he's faced some meaningful opposition from conservative politicians. On the other hand, while I don't think anyone would describe their philosophic approach to budget matters as "first cut taxes and then when looking at the spending side, focus cuts on programs for the poor rather than on corporate subsidies" but ever since the days of Reagan and Stockman it's consistently been the practice of conservative politicians to pay for tax cuts through a combination of debt and cuts to programs serving "weak clients" rather than "weak claims" on the merits.
That reality doesn't, on its own, discredit the other, less discreditable notion. But when we're talking about politics, the tenets of actually existing conservatism are the ones that matter. People who think there's some other notion of conservatism that would work need to first show they can make it have some influence over the conservative political party and the conservative movement before it makes sense to define "conservatism" by construing it as meaning something other than what the conservative politicians do.
[By the same token, e.g., there's some sense in which "liberals" -- people you might meet on the street or at your local left-of-center opinion magazine -- support adopting a less crazy attitude toward the "war on drugs" but whatever sense this is doesn't seem to extend Democratic Party congressional leaders or presidential candidates or translate into anything happening]