Separate thought process: the President of the United States doesn't need to have been born in America. The President only needs to convince people of that fact. It's really quite a reliable process. If a presidential candidate can't convince enough people of their legitimacy, the candidate won't be elected. Soviet spies taking office isn't much of an issue. Obama can and has proven beyond any normal requirements that he was born in Hawaii. If he wasn't, nothing would change. The only change comes about as a result of perception of his place of birth. The perception that his place of birth has not been proven is rather warped. Warped perceptions are a whole different matter that a presidential candidate can't cater to.
Luckily for McCain, he (also) had ample evidence that he was (not) born in America. Shut up; I know Panama counted on a technicality.