October is usually defined by crisp fall weather, Columbus Day weekend, and Halloween. Yet this year, the dates that may command more attention are the seven featuring political debates in the hotly contested US presidential and Massachusetts senatorial races.

Senator Scott Brown and Elizabeth Warren, his Democratic challenger, hold the second of their four-debate series Monday night at the University of Massachusetts Lowell. David Gregory, host of NBC’s “Meet the Press,” will moderate the hourlong face-off.