Most presidents become a joke at some point. It's a matter of when and how. Both points should concern this president. In Winston Churchill's words, "a joke is a very serious thing." Or it can be, when the joke is about a very serious thing. "Saturday Night Live" has long been a comedic benchmark. Last weekend, SNL took its first hard hit at President Obama. Fred Armisen, who plays the president, gave an Oval Office address: "When you look at my record it's very clear what I've done so far and that is nothing. Nada. Almost one year and nothing...