History is on the side of incumbent Republican Bruce Poliquin in the race for Maine’s 2nd Congressional District in the November election. But observers say his once-defeated challenger, Democrat Emily Cain, could benefit from the political shakeup of a high-stakes presidential race that’s expected to boost voter turnout in the general election. Both candidates are gearing up for a rematch of their 2014 race, in which Poliquin edged Cain by 5 percentage points.