Vattel. Jus sanguinis certainly, jus soli no. To be a Natural Born Citizen, you need to have satisfied both conditions.
Is he a citizen? Yes, unquestionably, by all means, and by any accepted definition.
The Founding Fathers, in their wisdom, clearly intended that the President be more, that he be that clearest and purest form of American, one who was both born here, and born of two American citizen parents. They recognized that he needed to be above any hint of foreign allegiance or entanglements.
Just suppose McCain had been elected: What would be his appropriate response should what happened in Honduras have happened in Panama?
ANY response he gave, whether he supported the Panamanian Constitution or the Panamanian Zelaya would be subject to endless second guessing and challenges. (A lack of a response would be a sign of weakness...)
If you are going to cite Vattel as the authority, notice that Vattel specifically exempts a nation's fighting men from the jus soli requirement.