The Clerk of the City while holding such office, and two persons by him appointed having the qualifications of a voter shall constitute a Board of Ballot Commissioners of which Board the Clerk shall serve as chairman. Ballot Commissioners shall be appointed between the fifteenth and thirtieth days of March in each year in which a general election is to be held, for a term of two years beginning on the first day of April next ensuing. They shall perform the duties of such Commissioners at all general, special and primary elections held in the Municipality during their term of office. A vacancy shall be filled in the same manner as an original appointment, but immediate notice of a vacancy shall, where necessary, be deemed compliance with the five-day notice provision.