The Plymouth Area League of Women Voters is sponsoring a debate Oct. 18 between candidates who will represent Kingston in the state Senate and House of Representatives. State Senator Therese Murray, a Plymouth Democrat and the Senate president, is running against Thomas Keyes, a Sandwich Republican, in the Nov. 6 general election. Keyes challenged Murray for the seat unsuccessfully two years ago. Representative Thomas Calter, a Kingston Democrat, and Debra Betz, a Plymouth Republican and a member of her town’s School Committee, are vying for the House seat. Attorney Alice Lague of Plymouth will moderate the debate, which begins at 7 p.m. at the Kingston Town Hall.