I keep thinking that Bush feels that he has to wait until after the election and some more of Iraq dies down and some troop shifts are made before he has the flexibility to deal with Iran.
I'm thinking that the Iranians know this too. It's to their benefit if they can make us move before we're ready. In fact so long as we're "out of prime position" this way with troops in places like Korea and spread out elsewhere in areas that are not too easy to deploy from, this is a prime time to hit us again on our own soil. Hence the warnings from Mossad1967.
Withdrawing to the Homeland, is a sure bet that they are looking at the next 911 and want to be able to respond; either to the borders or to the "HOT ZONES" of whatever type that may happen to be. AQ will want to strike and perhaps globally before we can marshal our defenses here. I don't think they really fear our DHS or federal agencies at least in the arena of combat. But they worry about our military forces, IMHO. They know that deployments have stretched us dangerously thin and that local, state and federal cops, in all likelihood won't fight to engage and destroy AQ forces here on home soil. SWAT guys will, but there are not legions of them to be had. Even SWAT will react to training and that's not combat. That may be a misperception on my part, but I'll bet AQ has the same mindset.
They're not sweating our LEO's. Oh they respect the intell guys that manage to sweep them up before they can strike! But in toe to toe war, I think THEY think they can outfight the cops. With noncombatants (American civilians) in the line of fire they may be correct. I remember a movie with that commie Clooney called The Peacemaker where a police sniper wouldn't take a greenlight on a terrorist with a suitcase nuke, because a little girl would have to die first. I'm afraid a lot of cops will react the same way.
My fear is that we blew the "pre-emptive" card with Iraq. Intelligence may have overestimated the probability of a counter-revolution against the Iranian clerics, placing them at a lower priority than Saddam Hussein.
I think it will be extremely difficult to play the pre-emptive card with Iran. Israel has a better hand to play than we do, given their direct vulnerability to the Iranian medium-range missile. As insane as it sounds, world support of the United States would probably vanish (these are indeed times of insanity) if we launched another pre-emptive war on Iran. As long as the Israeli trump card exists, I wouldn't expect the U.S. to strike Iran UNLESS - unless - a terrorist attack occurs on U.S. soil which can be pinned on Iran, or Iran's support of Al Qaeda. At that point, all bets are off.