One of the administration's articles of faith is that if we leave Iraq, al Qaeda will take over.
That is, frankly, a crock.
Consider this: when the US pulls out, Iraq will be dominated by the Shia. Bin Laden and his acolytes are radical Sunnites who have called the Shia infidels. True, there will be a substantial number of Sunni Iraqis, but the second word of that phrase is the most important: they are Iraqi. Al Qaeda is not--its members are mainly foreign.
Will al Qaeda cause trouble in Iraq even after the last American combat troops are gone? Very likely--although if it acts against fellow Arabs it will soon lose what shred of legitimacy it may have. But dominate the country? Never. And ultimately, its adherents will have to leave Iraq or be slaughtered.