One of the hallmarks of political campaigns in American history is that they are often nasty, brutish, and long. And they have been since the beginning. The contest between Thomas Jefferson and John Adams in the 1800 presidential election, for instance, was a bitter affair and resulted in a breach between the two statesmen that wasn’t healed for two decades. And virtually every campaign since has been filled with acrimony and insult and vituperation. So the question is why? Why can’t everybody just agree to be gentlemanly about the whole business, have polite and well-mannered debates, and let the people…...