The primary example of the past 20 years is Reagan (1980 and 1984) and the Gingrich Congress of 1994. The two Bush presidents were nowhere near as conservative as either of those men. Bush Sr. ran on Reagan's coattails, and lost his re-election against someone with almost no principles at all. George W. Bush barely squeaked into office in 2000, and probably only won in 2004 because the Democrats ran a dip against him.

With a few exceptions (national security for one) McCain is about as far from conservative as you can get and still be a Republican. I was reading something today (I can't find it now) about how he got "talked into" Palin as VP, and really wanted Lieberman (a Democrat).

It's no surprise that the Democrats are trying to discredit the very concept of conservatism. If they can manage to wipe the last vestiges of Reagan out of the GOP, they'll hold power forever, while the GOP tries to figure out why Republicans trying to be like Democrats can't beat a real Democrat.