I really wish the people would stop with this "Petraeus as Romney's running mate" nonsense. It's just as silly as considering Obama dropping Biden from the ticket. Waste of time and thread.
Defense is the GOP's weakest plank this election. Moral has BHO's gay marriage endorsement to rail against and Fiscal has the prolonged economic slump which Romney himself hopes to take advantage of. If he picks a Condi Rice or David petraues and capitalizes on the polarizing issue of Syria, then 269/270 doesn't seem too unrealistic for such a bland rental pol.
For the last time, there's a little problem preventing Petraeus from running for Vice President. He is an incumbent CIA Director and, by holding a government appointed office, he's legally barred from not only running, but also taking part in any political campaign. And, frankly, I can't see him suddenly quiting.
As of Condi, she's a living symbol of Bush administration foreign policy failures. I don't believe Romney would be that stupid to not realize that.
Beside, picking a defense/national security oriented figure wouldn't be good for Romney. His shot at winning is to make this election about economy and he should stay focused on internal affairs. Picking someone with defense/national security record would be a big, crying "I'm picking the guy, because I have no idea about foreign and defense policies, but I'm trying so hard to appear good on this".