The members of the board shall be citizens of high moral standards and recognized ability in their respective business or profession, who have resided in the state for not less than five years immediately preceding their appointment, and not more than one of whom shall be a resident of the same county or congressional district. At no time shall more than four members be of the same political party. No member of the board shall be connected, either as an official or as an employee, with any public, private, or denominational school, college or university, nor be the holder of or a candidate for any public office.