re: "John McCain Is A Mexican [Rumors On The Internets]" II
When in doubt, read the manual.
In this case, 7 Foreign Affairs Manual (FAM) 1131.6-2, "Eligibility for Presidency":
a. It has never been determined definitively by a court whether a person who acquired U.S. citizenship by birth abroad to U.S. citizens is a natural-born citizen within the meaning of Article II of the Constitution and, therefore, eligible for the Presidency.
b. Section 1, Article II, of the Constitution states, in relevant part that “No Person except a natural born Citizen...shall be eligible for the Office of President;”
c. The Constitution does not define "natural born". The “Act to establish an Uniform Rule of Naturalization”, enacted March 26, 1790, (1 Stat. 103,104) provided that, “...the children of citizens of the United States, that may be born ... out of the limits of the United States, shall be considered as natural born citizens: Provided that the right of citizenship shall not descend to persons whose fathers have never been resident in the United States.”
d. This statute is no longer operative, however, and its formula is not included in modern nationality statutes. In any event, the fact that someone is a natural born citizen pursuant to a statute does not necessarily imply that he or she is such a citizen for Constitutional purposes."
So the answer is. . . . that there is not an answer yet. Since this is America, and we still go by "That which is not specifically forbidden is allowed" rather than the totalitarian "That which is not specifically permitted is forbidden," my position is that until a court says an American citizen born abroad, who was a citizen from birth and not a naturalized citizen doesn't count as a natural born citizen, then he or she is natural born. And since the FEC has thusfar permitted the candidacy, I'm inclined to predict that this will constitute a precedent for any such candidacies in the future.