A lot of the Democrats, with the exception of the War in Iraq, ran as conservatives this time around. Those who think that this was a defeat for conservatism are dead run. It was yet another vindication for conservatism.
Bush has not taken "some" positions that went against the base. He's taken a lot of them.
General dissatisfaction with Republicans, whether because of the war (idiot left) or because of failing to stick to a conservative message (the right) hurt the good ones too, likely enough to make a difference in a close race.
The lesson from this is not to toss out the base, but to instead stick to the message which we promised when we did so well initially. A good, strong, conservative message, and more importantly, following through on that message, will beat the Left in the large majority of areas.
That should be "dead wrong", LOL.