Oh, for a good riposte.

Barack Obama's levity-free reaction to the now-famous New Yorker cartoon leaves one reluctantly wondering: Is he humor-challenged? Perchance, does he take himself too seriously for a nation of wits and wags?

So soaring has been Obama's rhetoric and so dazzling his smile that we've missed the possibility that the Illinois senator is less the lanky rock star and more the purse-lipped church lady, clucking his tongue in disapproval of the chuckling masses.

His campaign's angry reaction to the magazine cover shows a stunning lack of political dexterity. It wasn't always so.

In earlier days, Obama was self-deprecating and light of touch. But something happens as people get closer to Washington, as Obama himself has pointed out in other contexts. A popular story that Obama tells concerns a Las Vegas debate during which he was asked about his weaknesses.

Obama answered that he has trouble keeping up with paper, that his desk is a mess. OK, it wasn't knee-slapping hilarious, but it was honest and, therefore, endearing. A real answer from a real person.

In contrast, two of Obama's contenders, both Washington veterans, responded to the same question with the kind of painful earnestness that makes dogs cynical. As Obama recounts it, one of them said his biggest weakness was that "I'm just so passionate about helping poor people." The other said, "I'm just so impatient to help the American people solve their problems."

Ooph.

Obama continues the story: "So then I realize, well, I wish I'd gone last and then I would have known." (Laughter, applause.) "I'm stupid that way, I thought that when they asked what your biggest weakness was, they asked what your biggest weakness was. And now I know that my biggest weakness is I like to help old ladies across the street."

Now, that's funny. And there's a reason the other two candidates -- John "passionate" Edwards and Hillary "impatient" Clinton -- aren't leading the Democratic ticket.

Obama's self-deprecation was his most charming bit, but lately he is, well, less charming. He and his wife seem more like a finger-wagging principal and teacher tag team, with Michelle Obama promising that her husband will make us work harder when he becomes president. You get the feeling that should the Obamas take over, we'll all be staying after school. They used to call that detention.

Of course, John McCain isn't exactly a merchant of mirth. He didn't like the cartoon either, or so he said. Although his usual disregard for politically correct reverence is refreshing, his humor often seems not offbeat, but off-a-beat. Spontaneous jokes, such as his singing "Bomb-Iran-bomb-bomb-bomb," are actually less funny than the fact of his telling (or performing) them. Does he get it?

When I hear McCain "being funny," I'm reminded of a booklet of after-dinner jokes my father compiled to help pay his college tuition. The World War II-vintage jokes simply aren't amusing anymore. They belong to another time and place, another set of cultural markers, the common understanding of which is crucial to humor. Continued...