Last September, I attended a rapturous, early rally of Democratic senatorial hopeful Graham Platner in Portland, Maine.  Platner, a bearded, 41-year-old veteran and oyster farmer who is running for one of Maine’s two US Senate seats, seemed back then to have fallen from the skies. He announced his candidacy out of nowhere and, overnight, became the subject of long, frothy national profiles and gleeful political speculation. Seven months after I stood outside a brewery listening to him speak – with the midterm elections yet six months out, somehow – the Platner attention, the fascination, has not let up. Last Saturday,…