Not according to the US Department of State, at least. McCain was born on a US military base in Panama. Here is the language from their web site:
" c. Despite widespread popular belief, U.S. military installations abroad and U.S. diplomatic or consular facilities are not part of the United States within the meaning of the 14th Amendment. A child born on the premises of such a facility is not subject to the jurisdiction of the United States and does not acquire U.S. citizenship by reason of birth. "
As made clear under 7 FAM 1111.2, birth by US citizens confers citizenship by statute; only birth in the US confers citizenship through the US Constitution. So, if birth overseas, even in a US military base, does not qualify to grant citizenship by birth under the 14th Amendment, can McCain be a "natural born citizen" under Article 2 of the Constitution? Here is a
link to the article on the Department of State's site. Look for section 7 FAM 1116.1-4 (c).