Mass. Gen. Laws ch. 56, § 29

Whoever wilfully and without lawful authority hinders, delays or interferes with, or aids in hindering, delaying or interfering with, a voter while on his way to a primary, caucus or election, while within the guard rail, while marking his ballot or while voting or attempting to vote, or endeavors to induce a voter, before depositing his ballot, to disclose how he marks or has marked it, shall be punished by a fine of not more than five hundred dollars or by imprisonment for not more than one year.