I think they are just continuing a trend that was begun when the Republican party sold its soul to the social conservatives in the '80s. It caused a grand political realignment and brought them new success and relevance, but at what a cost.
Frankly, if the Republican Party (I guess to be fair I should call it the republic party like the ultra-rightists call the Democratic party the democrat party, lol) had a moderate wing anything like it used to, and voting Republican didn't mean I was supporting whack-jobs who think that I shouldn't have the right to exist, I would be a Republican. Moderate fiscal conservatism combined with moderate social liberalism? Sounds good to me and a good alternative to a Democratic party to which I am loyal, despite my disdain for liberal economic populism.
But I am a Democrat and a Democrat I will stay, until the Republican party excises the cancer in its midst. Which it won't do, because without the appeal to the crazies they can't put together enough votes to win. It's sad.