Candidates for town office will face off Wednesday at a forum in Cahill Auditorium at Town Hall. The event, scheduled to begin at 7 p.m., takes place on the last day residents can register to vote in the Nov. 5 election. While each nominated candidate has been invited to attend, only some of the town’s open seats are being contested. Voters will choose three councilors-at-large from four candidates, including incumbents Sean Powers and Charles Ryan, and will also pick between two councilor candidates from District 4 and three from District 5. Although three four-year seats on the School Committee are available, only two candidates qualified for the ballot; the remaining seat will be filled by a write-in candidate. Candidates at the forum Wednesday will have two minutes to introduce themselves, and will later speak directly with voters at assigned tables in the auditorium. The town has forbidden “direct, personal attacks on other candidates” during the forum, which is open to the public and will be broadcast on BCAM television.