As Maine's Senate race is heating up, Democrat Graham Platner made a controversial call after his primary rival Governor Janet Mills pulled out on Thursday. The progressive political outsider and oyster farmer will work to unseat Republican Sen Susan Collins now. The race is considered a must-win for Democrats, who need a net gain of four seats in November’s midterms to claim a Senate majority. Collins, 73, is widely viewed as the most vulnerable Republican up for reelection.Senate candidate from Maine Graham Platner speaks during a campaign event with the Maine AFL-CIO (Getty Images via AFP)Graham Platner's latest moveIt was...