You can also look at the EEOC summary related to Religious Discrimination, but summaries can be misleading.
http://www.eeoc.gov/types/religion.html
(f) The term ``employee'' means an individual employed by an employer, except that the term ``employee'' shall not include any person elected to public office in any State or political subdivision of any State by the qualified voters thereof, or any person chosen by such officer to be on such officer's personal staff, or an appointee on the policy making level or an immediate adviser with respect to the exercise of the constitutional or legal powers of the office.