ROVE, MANDATES, AND POWER. I agree with Matt and Garance (who has a new blog) regarding Karl Rove -- 2006 should finally put to rest the idea that having a better record running national elections than Bob "Losing Pitcher" Shrum makes you some kind of super-genius. I would add to Matt's analysis and say that even as it turned out, the 2004 outcome was in context highly unimpressive -- a wartime incumbent in a decent economy against a candidate nobody regarded as strong should do a lot better than the small margin Bush eked out. (The justly maligned Shrum actually had a better campaign, in that context.)
Matt also makes a good point, however, when he says that while Rovism was problematic as an election strategy it was more successful at achieving (admittedly appalling) policy ends. The one important insight Rove had is the fact that the "mandate" is a concept with no content and does not in and of itself produce any constraints. While the Broders and Kleins of the world were asserting that Bush had no "mandate" for change after his "election" in 2000 and would have to continue the Clinton legacy, Bush and Rove understood that your mandate was exactly as strong as what you could get the votes for in Congress, and they were successful at achieving their ends. It should be noted, though, that this pretty much stopped after Bush's re-election, with the disastrous decision to focus on Social Security privatization. While Bush and Rove were right that "mandates" aren't a meaningful constraint, Congress's power of the purse certainly is. Acting-as-if doesn't help you if you don't have the votes. (That is to say, asserting mandates is just as empty as assuming you'll be constrained by a lack of one.)
Even as a political force, Rovism had been spent before the 2006 elections. And a final note is that the major domestic accomplishment that can even plausibly be called "conservative" -- the massive tax cuts -- are likely to be undermined not only by the growth of government under Bush's watch but because of the too-clever-by-half gambit of inserting sunset clauses as a gimmick to underestimate their costs. It will be much easier for a Democratic Congress to let the cuts expire than to mobilize the votes to actively repeal them. Rove seemed to be betting that since Republicans would control Congress for a while this would be moot; fortunately for the country, he was in charge of running those elections.