Late last summer, with midterms consuming the attention of the political class, a group of GOP activists spent two days in Des Moines trying to convince their fellow Republicans that change was coming to their party. With eyes on 2016, they attended the Iowa State Fair, talked with newspaper editorial boards, and even ventured onto conservative talk radio. To cap it off, on the last evening, supporters gathered at 801 Chophouse, the upscale watering hole of the city's political elite, as if to announce their movement had gone mainstream. That it couldn't be dismissed as fringe any longer. Their issue,...