THE CHALLENGE TO AL QAEDA: All of the recent Al Qaeda--"bin Laden" pronouncements seem to be getting Old Media into a very jittery state. And it's doing wonders for America's hardware stores and duct tape sector.

It's possible/probable that Al Qaeda has already planned some sort of response to the start of an Iraqi attack. The question is, can they pull off a big attack, if not on a 9/11 scale, then something like Bali? I ask the question not because of any morbid curiosity, but because an attack on Iraq throws the gauntlet down for Al Qaeda, and unless they respond quickly, they will look enfeebled and irrelevant.

The fact is, it's extremely difficult to measure success in the war on terror. A stretch of months without a bombing could be due to improved counterterror tactics or because Al Qaeda is biding its time. However, these pronouncements, combined with the likelihood of war with Iraq, combined with skeptics claiming that such an attack will weaken our war on terror, provides what social scientists call a "crucial case" in testing the disparate hypotheses. Three possibilities:

1) No attack takes place during the war or its immediate aftermath -- this would support Bush's SOTU contention that we are winning the global war on terror.

2) A big attack takes place, but not on U.S. soil -- this would support the contention that homeland defense measures have had an appreciable effect in preventing Al Qaeda from repeating a 9/11 attack. However, it would partially undercut the contention that Al Qaeda's strength is waning.

3) Coordinated attacks take place, but not on U.S. soil. Same message as above regarding homeland defense, but a clear refutation of the "weakening Al Qaeda" hypothesis.

4) A big attack takes place on U.S. soil -- this would support critics' contentions about the war on Iraq triggering such attacks, as well as raise some disturbing questions about the quality of homeland defense. It would certainly demonstrate Al Qaeda's potency.

UPDATE: This report suggests that perhaps the proximate threat from Al Qaeda has been exaggerated.