There has been much discussion about whether votes in this next election will be counted securely.
Every state has rules about what poll observers can do at the polls and how votes can be challenged. Here are the rules for your state:
Massachusetts The state committee of a political party may appoint a person to act as a challenger of voters at any polling place in the commonwealth at a state election (Mass. Gen. Laws ch. 54, § 85A). To achieve the legal requirement that the election be held in public view, observers shall be allowed inside the polling place, outside the guard rail, unless they are disorderly or obstruct the access of voters. Observers may keep notes including marked voting lists. If there are so many observers in the polling place that they obstruct voters, they may be asked to cooperate in collecting information. The warden may exclude from the polling place any person who is disorderly or who obstructs the access of voters. (950 C.M.R. § 54.04(22a).
Any election officer or other person may challenge a person's right to vote for any legal cause (Massachusetts Secretary of State Election Day Legal Summary).