Well, there is this argumnet:
Why Senator John McCain Cannot Be President: Eleven Months and a Hundred Yards Short of Citizenship
Abstract:
Senator McCain was born in 1936 in the Canal Zone to U.S. citizen parents. The Canal Zone was territory controlled by the United States, but it was not incorporated into the Union. As requested by Senator McCains campaign, distinguished constitutional lawyers Laurence Tribe and Theodore Olson examined the law and issued a detailed opinion offering two reasons that Senator McCain was a natural born citizen. Neither is sound under current law. The Tribe-Olson Opinion suggests that the Canal Zone, then under exclusive U.S. jurisdiction, may have been covered by the Fourteenth Amendments grant of citizenship to all persons born . . . in the United States. However, in the Insular Cases, the Supreme Court held that unincorporated territories were not part of the United States for constitutional purposes. Accordingly, many decisions hold that persons born in unincorporated territories are not Fourteenth Amendment citizens. The Tribe-Olson Opinion also suggests that Senator McCain obtained citizenship by statute. However, the only statute in effect in 1936 did not cover the Canal Zone. Recognizing the gap, in 1937, Congress passed a citizenship law applicable only to the Canal Zone, granting Senator McCain citizenship, but eleven months too late for him to be a citizen at birth. Because Senator John McCain was not a citizen at birth, he is not a natural born Citizen and thus is not eligible to the Office of President under the Constitution.
That's a huge leap.