ON first watching Hillary Clinton’s recent “It’s 3 a.m.” advertisement, I was left with an uneasy feeling that something was not quite right — something that went beyond my disappointment that she had decided to go negative. Repeated watching of the ad on YouTube increased my unease. I realized that I had only too often in my study of America’s racial history seen images much like these, and the sentiments to which they allude. I am not referring to the fact that the ad is unoriginal; as several others have noted, it mimics a similar ad made for Walter Mondale...