Krauthammer:

But I remain puzzled. Let's say that al Qaeda is so badly hurt that it cannot organize another Sept. 11 with 19 hijackers, four planes and years of training. Yet how much training, how much planning can it take to pack a few trucks with explosives and blow them up in crowded shopping malls? Considering the economic and psychological havoc that would wreak, why haven't they done it?

After all, Timothy McVeigh did not need a huge terror apparatus to kill 168 people in the heartland of America. It takes but a primitive level of organization to do that. It is hard to believe al Qaeda is not capable of doing the same. So why hasn't it?

The other explanation is that it is a matter of pride. Having pulled off the greatest terrorist attack in the history of the world, al Qaeda does not want to sully its reputation by resorting to the cheap car bomb.

Politically, the fact that we haven't been attacked again is a huge issue. Bush would be idiotic to use the issue but it proves that what he has done works. I believe that luck, the systematic dismantling of al-Qaeda, the Iraq war, luck, and more vigilance at home are the key factors.