Not exactly the greatest of surprises. He was going to get (as Mike Allen put it) "shellacked" by the hard right.
I agree with Allen that this probably isn't going to help him. Incumbents are going to be under fire in November; an incumbent without the benefit of party identification is only going to be that much worse off. It was inevitable—Republican primaries actually mean something—but he's still not in good shape. He might lose the seat, and the Dems might win it.
In the long run, though, this only benefits the conservatives in the Republican party. They've demonstrated their power. They've pushed the party to the right, and they've made the politicos that much more worried about them. When the Republicans regain control, that's going to ensure that conservatives get much more of a say than they would otherwise.
For progressives this should prove...instructive. If they're willing to learn the lesson.