I can't remember who said it, or where I saw it, but I think the following is an interesting point: Republicans fear their base, and Democrats hate their base. I think that it is true on the whole. The McCain re-election campaign is an excellent example. That man abandoned almost everything that made him interesting in 2000 and mildly palatable in 2008, and all because of a primary challenge to the right. McCain knew he had to abandon stated positions that might have angered AZ primary voters (fear). Columnist Michael Smerconish wrote an article at Salon talking about the purging of the so called Republicans in Name Only, and the national party is going right along with that effort (fear).
Meanwhile, the Democratic party, from President Obama on down have been making it a point to bash the Democratic base (here is the latest). It's incredible to witness. I cannot imagine a GOP candidate ever telling member of its base to "stop whining." I would hazard a guess that if the Democrats really suffer a major blow in November, then it will be because they worked so hard to try to show voters likely never to vote for them that they can stand up to their "crazy" and "radical" base. And I am sure that without a hint of irony, the Democrats, should big losses come their way, will blame their base, and not themselves.