Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 52, § 6

A vacancy in the office of chairman, secretary or treasurer or in any other office, notice of the filling of which must be filed under the provisions of section five, of a city, ward or town committee or in the membership of a ward or town committee shall be filled by such committee from among the enrolled members of the party resident in such city, ward or town, and a statement of any such change shall be filed as in the case of the officers and members first chosen. If any member shall change his residence from the city, ward or town in which he was chosen to fill said vacancy, he shall cease to be a member at the end of the calendar year during which said residence is changed.