For many Republicans, the bright, golden haze of Election Day is marred by a thunderhead on the horizon -- the increasingly erratic political interventions of Sarah Palin. In the past, Palin embodied the populist style of the Tea Party movement while espousing a fairly mainstream Republican ideology. On economic, social and foreign policy, Palin seldom strayed from a simplified, popularized Reaganism. The mama grizzly may have been ferocious, but her talking points came from the Heritage Foundation instead of from darker corners of the right. But this election season has called that perception into question. Palin's endorsement of Christine O'Donnell...