The Republicans really do have a problem with the conservative strategy of taking the maximalist position on things. First up, electoral consequences.
You don't need a political scientist to tell you this one: conservatives are rapidly making it impossible for Republicans to win very many elections in large portions of the nation. By now everyone has heard the latest news from NY-23, in which the moderate Republican candidate, who dropped out yesterday, has now endorsed the Democrat. This time, what all the pundits are telling you is correct. This is at best a major problem for Republicans, and at worst a complete disaster. Not, of course, the single seat, but because of the continuing incentives and lessons that future candidates, potential candidates, and activists are going to take from it. Future candidates are going to find it necessary to stick to extreme conservative positions in order to secure the nomination, even if they appear to have the full backing of the party establishment. Potential candidates are going to be less likely to run, because they can't trust promises of full support from the party establishment. And activists are going to learn the lesson that they can take down establishment candidates. We're going to see more of this, not less, next year.
And it's going to cost the Republicans seats. I should say: it's going to continue to cost Republicans seats. I'm not making any predictions about this one, although as I read Charles Franklin's analysis and then add Scozzafava's endorsement, it doesn't look bad for Owens, the Democrat. Still, special elections are notoriously difficult to predict, and the polling on this one leaves the outcome very much in doubt. However, overall, this is certainly costing Republicans seats.
Of course, that's balanced, for conservatives, by intense loyalty among those who do win office. You can see that in NY-23. Without conservative support for Hoffman, the seat would have gone to a moderate, pro-choice Republican. Now, it will either go to a mainstream Dem or to a conservative candidate who will caucus with the Republicans. That's what's been happening nationwide, which is part of the reason that there are only 40 Republicans in the Senate, but also why most of those 40 are intensely loyal conservative votes.
Overall, that's bad news for Republicans, and I would argue that it's bad news even for conservative Republicans. In the House, by far the most important vote anyone casts is the vote to organize the House (that is, the vote for Speaker). It's going to be hard to win very many of those votes if the Republicans refuse to compete at all in marginal districts.