This AP story tells us that voters have become more ideological, but to a much greater extent on the GOP side, but it also says that House Republicans' fear of primary challenges is largely unwarranted:
... many House Republicans [have] only one prerequisite to assure their re-election: Never give a hard-charging conservative enough room on the right to mount a viable challenge in the primary.So every Republican in the House is afraid of a primary challenge from the right, but primary challenges hardly ever work? Reminds me of the way everyone in Congress is afraid of the NRA, even though statistics show that NRA spending doesn't actually win races.
In practice, the task doesn't seem so hard. Only six House Republicans lost their re-election primaries last year. Half of them fell to fellow incumbents in redrawn districts that forced two colleagues to oppose each other. The other three lost to challengers with strong tea party support.
Of course, maybe there aren't very many successful primary challenges in the House because House members have simply given up on moderation, and are meekly doing as they're told by the far right -- it's hard to know how many of these people would survive if they dared to deviate from conservatively correct thinking. And it's certainly more of a risk for Republican senators, as Bob Bennett and Richard Lugar learned -- if you're running statewide, even in a deep red state, you have to be mindful of at least some moderates, so you might deviate from the dogma once in a while and pay a price, whereas many House districts are so red that you'll nevereven consider straying.
But in any case, in the House it seems as if the primary threat is overrated, and teabagger rage, like NRA rage, might appear more dangerous than it actually is. But this is D.C. we're talking about, where conventional wisdom is always truth, so I don't expect anyone ever to reality-test this premise.