Because McCain's parents were citizens when he was born, McCain IS a natural born citizen (no matter where he was born). This is the law: 8 U.S.C. Sec. 1401.
Significantly, however, Congress, in which a number of Framers sat, provided in the Naturalization act of 1790 that ''the children of citizens of the United States, that may be born beyond the sea, . . . shall be considered as natural born citizens. . . .'' [Act of March 26, 1790, 1 Stat. 103, 104. See Weedin v. Chin Bow, 274 U.S. 657, 661 -666 (1927); United States v. Wong Kim Ark, 169 U.S. 649, 672 -675 (1898). With minor variations, this language remained law in subsequent reenactments until an 1802 Act, which omitted the italicized words for reasons not discernable. See Act of Feb. 10, 1855, 10 Stat. 604 (enacting same provision, for offspring of American-citizen fathers, but omitting the italicized phrase).]
McCain is either a "natural born citizen" [hint: he is] or a "naturalized" citizen [hint: he's not]--or do you contest his citizenship entirely?
Weedin v. Chin Bow (1927) holds that "at common law the children of our citizen born abroad were always natural born citizen from the standpoint of this government."
It is the consensus of scholars that foreign born children of Americans are natural born citizens. And that would mean that McCain would certainly qualify.