Discussing Portland’s rental housing crunch at a forum Thursday are, from left, Mayor Ethan Strimling; Brit Vitalius, a real estate broker and the president of the Southern Maine Landlord Association; Richard Barringer, professor emeritus of community planning and development at the University of Southern Maine; Grace Damon, co-chair of the Portland Tenants Union; and Press Herald Metro Editor John Richardson, who moderated the forum.