Mass. Gen. Laws ch. 39 § 14
At every town meeting when moderators are not elected for the term of one or three years, a moderator shall first be elected. The election of a moderator at a meeting for the choice of town officers shall be by ballot, and the voting list shall be used thereat.
Any town or district which has so voted or hereafter so votes may at any annual election of town or district officers elect from the registered voters thereof by ballot a moderator to preside at all town or district meetings. His term of office shall begin as soon as he is qualified, and shall continue until the next annual town or district meeting and until his successor is qualified. Any town or district which has elected a moderator for the term of one year shall thereafter elect a moderator at every annual election of town or district officers, unless the town or district votes to discontinue the electing of moderators for said term.
If a vacancy in the said office occurs during any term, it may be filled by the voters of the town or district. If a moderator so elected is absent, a temporary moderator may be elected.
In towns or districts where official ballots are used, the vote to elect a moderator for the term of one year shall be taken at a meeting held at least thirty days before the annual town or district meeting at which the vote is to become operative; and at the first annual meeting after the town or district has so voted a moderator shall be chosen as herein provided to serve at that meeting, and the moderator elected on the official ballot at that meeting shall act at subsequent town or district meetings until his successor is qualified.
At every town or district meeting until a moderator or temporary moderator is elected, the clerk of the town or district shall preside; but if he is absent or if there is no clerk, the chairman of the selectmen or prudential committee or body exercising similar powers, if present, otherwise the senior member present in point of continuous service, shall preside; but if no selectman or member of said committee or body is present, the justice of the peace calling such meeting, if the meeting is so called, shall preside. Such presiding officer shall have the powers and perform the duties of a moderator.
If, as provided for in section ten, a town meeting is held in separate places equipped with a public address system and loud speaker facilities, the moderator may appoint an assistant moderator to preside at each place of meeting whereat the moderator is not present. The assistant moderator shall have all the powers vested by law in the moderator to preside at and regulate the proceedings in the meeting at which he presides except that he shall not recognize any citizen desiring to address the meeting except after first obtaining permission of the moderator.
The word "district", as used in this section, so far as apt, shall be construed as it is defined in section one A of chapter forty.
Mass. Gen. Laws ch. 39, § 14