One thing the terrorists love to do is to TAKE CREDIT for things. In a recent interview with some British Islamists, the guy said that the elections in Spain PROVED that Terrorism worked. So with out situation, they'll call for the ouster of Bush or whatever. When and IF the election goes badly for Bush, they'll point and say "see? We controlled them, it is a huge win for us!". This is all for recruiting purposes. If the election goes well for Bush, they just slink away as usual...
I agree that they'll just stay mum if Bush does well, but the problem is that they were right on Spain - terrorism did work, because nobody thought Zapatero and the Socialists had any chance of winning - until the day after March 11. In this case, it wasn't AQ that capitalized on the attack, however, but the Spanish left, which succesfully "blamed" Aznar for it. The same thing would happen in the US this time around with any new terrorist attack.