Democrat Chellie Pingree’s two challengers seemed to take more shots at each other than the incumbent during a Monday debate in the race for Maine’s 1st District U.S. House seat. Independent Marty Grohman, a state lawmaker from Biddeford, interjected during the very first question posed to Republican Mark Holbrook, setting the tone for a night that included several mid-question arguments between the two. Monday’s hourlong debate, hosted and televised by Portland NBC affiliate WCSH 6, was the second of three scheduled during the campaign, following one last week hosted by ABC affiliate WMTW.