The Constitution (Article II, Section I) on the eligibility requirements for the Presidency:
No person except a natural born citizen, or a citizen of the United
States, at the time of the adoption of this Constitution, shall be
eligible to the office of President; neither shall any person be
eligible to that office who shall not have attained to the age of
thirty five years, and been fourteen Years a resident within the United
Now maybe Mitt Romney has his own personal version of the Constitution, or he's just stupid, but in his version it apparently says you have to believe in God. Granted, everyone who's had the job has at least professed to believe in God (and some of them act like the Devil) but it's not a requirement.