The Obama New Yorker cover
This comes on the tail of this interesting New York Times article about how difficult it is to make jokes about Obama. The overall point is, "He doesn't have any flaws or buffoonlike characteristics." This is true to an extent. It's certainly a million times easier to make fun of Bush or Cheney or any of a hundred politicians who blurt stupid or insane things every time they open their mouths, or to make fun of smart politicians (like Bill Clinton back in the day) by focusing on their physical or cultural traits (like Bill's redneck background, his overeating, or his skirt-chasing tendencies).
But the New York Times article does the Daily Show a disservice, because despite their quotes to the contrary, they've gotten the right Obama take from the beginning: their joke is that he's the Messiah. He walks on water. He can heal the blind. It's hilarious. Obama himself said in one of his early TDS appearances, "Jon, the only person who is more overrated than me...is you."
The reason you can't make fun of his blackness, it seems to me, is precisely that there's not enough discernible blackness (at least in terms of cultural signifiers) to register as caricaturable. If he wore the occasional dashiki or if Michelle wore her hair in a natural, there'd be something to work with. But Barack's blackness has more to do with his background than anything relating to his present identity. It'd be like making fun of Ted Kennedy for being Irish.
Humor comes from using alternate logic; another way of seeing things that makes internal sense one way while being absurd in another. When I heard Rush Limbaugh's song "Barack, the Magic Negro," the main problem with it (aside from its attempt to turn Jesse Jackson into Stepin Fetchit) is that it didn't even get the target right. You can't make fun of Barack by saying, "Barack is black and black people have bad grammar and listen to rap." It's too much of a leap to make, and only a blinkered racist like Limbaugh could make it.
The way you make fun of Obama is to say, "He's too good to be true; he's so nice he'll get us all killed; he's an arrogant prick whose shit doesn't stink." These are images that actually fit with the guy we've all seen, which is why this cartoon works as an Obama slam. It even makes fun of his ears.
Anyway, this is the best article I've read about the Obama New Yorker cover. It's short but punchy. Enjoy.