He wouldn't have been able to run if he wasn't a natural born citizen
I would imagine they actually check a candidates qualifications. There is probably a highly over-payed team that just does that.
It was McCain's job to hire that team do that. McCain did not want to bring up the fact the he was not born in the US (either) Although he, born in Panama he did have TWO parents that were US citizens, and was born on a US military post making him a "natural born citizen", under US law at the time.