NEW YORK — It's always risky to appear onstage with a comedian. Not only are funny guys funny but they're aggressive.

Indeed, humor is nothing but aggression harnessed and saddled — and nobody today rides that horse as well as Jon Stewart.

So what was President Obama thinking when he submitted to a nearly 30-minute interview with the Comedy Central star? He was thinking, of course, that he could rekindle some of the love with his base. Seventy-four percent of Stewart's audience falls into the 18-49 demographic otherwise known as — money.

Dude.

As others have noted, Stewart is a superb interviewer. No surprise there. The funniest people are also often the smartest people in the room.

Stewart asked all the right questions and managed to get the president to answer most of them. Should he have called the president "dude"? As a matter of decorum, the short answer is no. But in the context of the moment, who could resist?

Stewart had just asked Obama how he could square his campaign mantra of "change" with hiring economic advisers such as Larry Summers, who looks the same as those who had served in previous administrations. In response, Obama said that Summers had done a "heck of a job."

Whereupon, Stewart said, "You don't want to use that phrase, Dude."

Everyone got the joke. George W. Bush used the same words to commend Michael "Brownie" Brown after his disastrous performance as head of the Federal Emergency Management Agency following Hurricane Katrina. Translation: You're fired.

Everyone got the joke, that is, except for Obama. He got it eventually, after seeing the "oops" expression on Stewart's face, but he couldn't

take the joke. There's a world of difference.Instead of laughing at himself, he turned to the audience — a beat too late — and said, "Pun intended."No, it wasn't. Anyone watching could see that. He slipped. Obama is a nice guy and he was trying to say something nice about Summers, and "heck of a job" just tumbled out. No big deal. We get it. Stuff happens. But Obama couldn't roll with the gut punch.In that, among other moments, Obama revealed his fatal flaw. He has no sense of humor. He might be able to laugh at a joke. He can even tell one, as he demonstrated at the last White House Correspondents' Association dinner. Whoever wrote that script should send his resume to Comedy Central. Oh, wait, some of the writers

do work at Comedy Central.No, what Obama revealed was that he has no sense of humor about himself. This is utterly huge.It is entirely appropriate that the president take his job seriously. And no one would urge Obama (or anyone else) to try to be funny with Jon Stewart. He's the funny guy and producers doubtless remind guests of that fact. A good guest on "The Daily Show" is expected to be the straight man so that the comedian has some place to go with the material. I'm sure there's a Rolodex of "bad guests" who tried to out-funny the comedian.But it is imperative that leaders not take themselves too seriously. What should Obama have done instead? How about saying: "I can't believe I just said that"? Or, "Oy!"? Whatever. Anything to signal to the audience that, "Oh, well, I'm human."But Obama isn't very good at human. His smile is a beam of light, but too often it seems to turn on and off with a switch. Missing is the spontaneous response that says, dare I say it, "I'm you." (Pun intended.) More often, Obama comes across as a body snatcher. Good choice of pods, but we might need to add a little juice to the "emotion" grid.Like a majority of Americans, I like Obama. He seems to be a thoroughly decent guy, but he's more suited to chess than schmooze. You can almost see him calculating his answers, even hinting at admiration when Stewart made a good comeback. He all but says, "Nice move."Cutting the president some slack, we might acknowledge that these are tough times. Agree or not with his policies, Obama has had a very tough two years. The media are relentless. So are the Republicans.But in the human game we call life, victory and failure are respectively sweeter and less bitter if one is able to laugh at one's very own self.Heck of a job, Mr. President.Kathleen Parker is a columnist with the Washington Post Writers Group.