As the 2016 election campaign attests, the Grand Old Party-once moderate and even magnanimous-has fallen into a prison of its own making when it comes to presidential politics. After the debacle of the George W. Bush presidency and the rout of the Romney candidacy, Republicans said they must broaden their base, become more inclusive, and return to the warmth of Reagan idealism. Instead, what we have is a bitter, backbiting, and race- and gender-baiting...