No person holding any office, place, position, or employment subject to civil service, shall contribute to any political fund or render any political service to any person or party whatsoever, and no person shall be removed, reduced in grade or salary, or otherwise prejudiced for refusing so to do. No public officer, whether elected or appointed, shall discharge, promote, demote, or in any manner change the official rank, employment, or compensation of any person under civil service or promise or threaten so to do for giving or withholding, or neglecting to make any contribution of money, or service, or any other valuable thing, for any political purpose.