Questions have been raised about the eligibility of both candidates, especially Obama, and there should be no problem in verifying the information. What if Obama's mother had renounced her citizenship? For McCain, being born on a US military base is not the same as being born in the USA. In view of the outlandish decisions by the Supreme Court, it would come as no surprise if it said McCain did not meet the criteria.
But BOTH of his parents were US citizens, unlike Obama.
This issue also came up in 1968, when George Romney (Mitt's dad) ran for the GOP nomination. George Romney was born in Mexico of American parents. The consensus then was that the fact that both parents were US citizens meant that he qualified as "natural-born," even though he was born outside the US.