Hillary Clinton has finally found Barack Obama's weakness.

"Clearly we need to do something so that our party and the people can make the right decision" about who to nominate, Clinton told reporters after her speech to the Pennsylvania AFL-CIO convention in Philadelphia. "I am challenging Sen. Obama to a bowl-off. A bowling match. Right here in Pennsylvania -- winner take all."

It would be a winning strategy; you can debate who's stronger on the issue, who's more electable, who competes best with John McCain, but it is simply not possible that Clinton bowls worse than Obama, who tried out his skills as a kegler in Altoona Saturday night. He was, indisputably, terrible, sending his first two tries wide right and scoring a 37 through seven frames before he quit. To be fair, I haven't seen Clinton bowl. But I watched Obama's entire painful game up close, and I doubt it could be duplicated.

So Clinton found herself with an irresistible April Fools' play. "It's time for his campaign to get out of the gutter," Clinton said this morning, earning actual laughs from the press, not the sort of polite, "well, at least they're trying" chuckles that many politicians get for their jokes.

Of course, she milked it a bit too much. First she tried to keep the gag on message: "When this game is over, the American people will know that when that phone rings at 3 a.m., they'll have a president who's ready to bowl on Day One." Then she hit us over the head with the bowling metaphors: "Let's strike a deal, and go bowling for delegates. We don't have a moment to spare." (Italics added to underscore forced puns.)

So far, no April humor from the Obama campaign, though a pool report from Allentown, Pa., reported he was in a good mood even without any attempted pranks. Obama will speak to the AFL-CIO Wednesday morning.