The City Commission shall appoint a City Manager, who shall be the administrative head of the municipal government, subject to the provisions of this charter, under the direction and supervision of the City Commission, and who shall hold office at the pleasure of the City Commission. He shall be appointed without regard to his political beliefs, but solely on the basis of his executive and administrative qualifications, and need not be a resident of the City at the time of his appointment. During the absence or disability of the City Manager, the City Commission may designate some properly qualified person to perform the duties of the office.