The League of Women Voters of Lexington will host a forum allowing residents to discuss the issues with candidates for Town Meeting and townwide offices Thursday at 7 p.m. in the science lecture hall at Lexington High School. With the official ballot closed for the March 4 annual election, the only townwide contest involves Nancy Corcoran-Ronchetti and Richard McDonough vying for a seat on the Planning Board. There are also more candidates than Town Meeting positions available in precincts 4, 6, 7, and 9, according to sample ballots posted on the town’s website, www.lexingtonma.gov. Tuesday is the last day to register to vote in the election. The candidates forum will begin with Town Meeting members, followed at 8:30 p.m. with candidates for townwide offices. Selectwoman Deborah Mauger and Joseph Pato, a Town Meeting member who has served on the town’s Appropriations Committee, are the only candidates for two seats on the Board of Selectmen, according to the town clerk's office, and incumbents Alessandro Alessandrini and Margaret Coppe are running unopposed for the School Committee. Deborah Brown is unopposed for reelection as moderator.