Mass. Gen. Laws ch. 54 § 13
Such election officers shall be enrolled voters so appointed as equally to represent the 2 leading political parties, except that, without disturbing the equal representation of such parties, not more than 1/3 of the election officers not representing either of them may be appointed. The warden shall be of a different political party from the clerk, and not more than one half of the inspectors shall be of the same political party. In each case the principal officer and his deputy shall be of the same political party. The preceding party representation requirements of this section apply only if the chairman of the city or town committee of each political party or the chairman of the state committee of such party files with the registrars lists of enrolled members of the party who desire appointment as election officers in accordance with the provisions of sections eleven B and twelve. Except as otherwise provided in sections eleven and twelve, every election officer shall hold office for one year, beginning with September first succeeding his appointment, and until his successor is qualified, or until his removal; provided, that election officers appointed to count and tabulate votes shall serve at such primaries or elections and at such times as shall be designated by the appointing authority. An election officer may be removed by the mayor, with the approval of the aldermen, or by the selectmen, after a hearing, upon written charge of incompetence or official misconduct preferred by the city or town clerk, or by not less than six voters of the ward, or, in a town, of the voting precinct where the officer is appointed to act.
Mass. Gen. Laws ch. 54, § 13