Section 6A. If an elected state, city, or town officer is to be retired on or before the next regular election by reason of superannuation before the completion of the term of office to which he was elected, thereby causing a vacancy in said office, such vacancy shall be filled at said regular election as provided by law for such office.

The retiring authority shall notify the county commissioners, mayor and aldermen in cities, or the selectmen in towns, as the case may be, of the impending retirement of such elected officer at least six months preceding the next state, city, or town election, as the case may be.