...I would venture that this is the "August Surprise" unfolding in front of us right now in the NYC area.  I would expect that some "thwarted terrorists" will abandon their "explosives-laden" truck and escape with their lives while the "authorities"  sieze the evidence to great huzzahs from the SCLM, all nicely timed for the Convention.  Perhaps the "explosives-laden truck" will conveniently detonate in a location that causes no damage but is clearly heard exploding by millions of people in the Metro area, with some "amateur" mini-cam footage by a lucky citizen who happens to be at a Little League game as the truck goes by and detonates. They could probably come up with some spare "DNA evidence" scraped from the wreckage that would point to persons with semitic DNA, such as Arabs.  This scenario would be child's play to create, and the "enhanced terror alert" is merely the opening overture to the production to follow in time for the Convention and national attention in which to point out what a great job they are doing to protect us.

Ok, now I'm taking off my tin-foil hat, but if this is what happens, or something similar, I'm gonna have to say "I told you so!"