Oval Newlywed Game MAUREEN DOWD New York Times

The etiquette breach was not widely noticed, swallowed by the cacophony over the economy.

But Joe Biden no doubt felt the sting when Barack Obama dissed him again in public.

The new president is so elegant, and so full of comity, even to his foes, that when he is simply a tad ungracious, it jumps out.

At his news conference last Monday, Mr. Obama was asked by Fox's Major Garrett about the vice president's startling assertion that even if he and the president do "everything right," "there's still a 30 percent chance we're going to get it wrong."

Admittedly, it must be an adjustment for the president, a detached observer who "travels light," as friends put it, to be yoked to such a garrulous social animal.

It can't be easy for someone with a highly defined superego to be bound to the wacky Biden id, for one so disciplined to be tied to one so undisciplined, for a man so coolly unsentimental to be paired with someone so exuberantly sentimental.

And yet, the minute the president began to laugh and answer Garrett, I feared Joe would be the butt.

"I don't remember exactly what Joe was referring to," said Mr. Obama, who couldn't resist adding, "not surprisingly."

It was the "not surprisingly" that was surprisingly snarky.

The president had already used his "disappointed parent" routine with Mr. Biden in public, looking reproachful and tapping Joe on the back when he made a benign joke, as he swore in White House staffers, about his memory not being as good as Chief Justice John Roberts's. Chastened, he called Justice Roberts afterward to apologize.

After the election, when Mr. Obama made a mild joke about Nancy Reagan and séances, Mr. Biden, who was on stage as well, did not wince at his partner in public or tap him like a strict nun.

When Mr. Biden indulges in his rhetorical overkill of repeating the same phrase three times — the proud men and women of Scranton, he said at a recent appearance with the president, "wanted the government to understand their problem, to understand their problem, be cognizant of the problem" — Mr. Obama has an air of suppressed annoyance, like an editor dying to take a red pencil to a long-winded writer. (It's an air you never see when the president appears next to more like-minded, self-contained souls like Tim Geithner.)

Mr. Biden's stream of consciousness can be impolitic. Politico's Glenn Thrush refers to "the human political polygraph that is Joseph Robinette Biden." It can also be bracingly honest.

Joe is nothing if not loyal. And the president should return that quality, and not leave his lieutenant vulnerable to "Odd Couple" parodies.

On a recent "Saturday Night Live" skit, Jason Sudeikis's Biden leaned over Fred Armisen's Obama, to tell Americans: "Look, I know $819 billion sounds like a lot of money. But it's just a tip of the iceberg."

Armisen's clenched Obama murmurs: "Couldn't pick Hillary. I just couldn't."

Gawker, a media gossip blog, translated Monday's Garrett-Obama exchange this way:

"Uh, Mr. President, Joe Biden said something yesterday about how you two will eventually destroy the world, forever. Care to comment?"

"Oh, that's just the vice president. We all know he's mentally unbalanced, right, guys? Ha ha ha ha. But seriously: He's nuts, please keep him away from sharp objects."

Obama advisers say that the two men get on well and that the president wants his second's candid advice. Mr. Biden considers Mr. Obama inclusive.

But some aides joke about the care and feeding of Mr. Biden's ego, and kid about the way the vice president clings to the president's schedule. Mr. Biden puts out guidance about his schedule — a refreshing change from the black hole of Cheney.

(He has also added a sitting area in his office, something the unilateral Cheney never needed, and has turned up the temperature in the vice president's house from the chilly Cheney-mandated 62.)

Obama aides say the president went out of his way to stroke the vice president — who felt he helped interpret the exotic Obama for the hoi polloi during the campaign — by putting him in charge of a middle-class working families task force.

Still, the president should brush up on his Jane Austen. When Emma Woodhouse belittles Miss Bates, an older and poorer friend, at a picnic, Mr. Knightly pulls her aside to remonstrate. "How could you be so insolent in your wit?" he chides, reminding her that it is unfeeling to humble someone less fortunate in front of others who will be guided by the way she behaves.

That's how it works ... not surprisingly.