Mary Kate Cary of U.S. News writes:
In fact, no sitting president has ever appeared on any comedy show. Richard Nixon did “Sock It To Me” on Laugh-In as a candidate for president—despite the objections of his staff, according to Nixon speechwriter Pat Buchanan—and Bill Clinton did the Arsenio Hall Show, but also as a candidate. President Bush #41 went on Saturday Night Live with Dana Carvey, but only after he left office. There’s a reason presidents don’t do comedy on television, especially in tough times.
Well, Gerald Ford taped a cameo appearance to say “Live From New York, It’s Saturday Night”, to air at the top of the show when his press secretary hosted an early edition of Saturday Night Live in April of 1976. Of course, foreshadowing the incipient partisanship of today’s NBC, the writers of the show later admitted, “The President’s watching. Let’s make him cringe and squirm.”
Somehow I doubt that Jay Leno, whose politics are remarkably simpatico with President Obama’s, despite his everyman image, will allow his writers to wreak such havoc.
Update: Further thoughts from Red State.com.