No person shall be qualified to serve as an election officer who shall hold, or shall within two months have held any office, appointment or employment in or under the government of the United States, or of this State, or of any city, or county, or of any municipal board, commission or trust in any city, save only notaries public and persons in the national guard or in a reserve component of the armed forces of the United States; nor shall any election officer be eligible to any civil office to be filled at an election at which he shall serve, save only to such subordinate municipal or local offices, below the grade of city or county offices, as shall be designated by general law.