For nearly two months, Graham Platner’s bid for the U.S. Senate was marked by momentum and bravado as the political newcomer drew big crowds to his town halls and he channeled Democratic voters’ hopes for a newer, brasher kind of candidate. During an interview in late September, he said, “I’ll just say, it’s been very surreal.” Reality has arrived over the past week. Now comes a test of Democratic primary voters' risk aversion.