New polling this week found Democrat Graham Platner leading Republican Senator Susan Collins 48 percent to 39 percent among likely Maine voters, signaling a competitive midterm election as the veteran and oyster farmer also posted a commanding primary advantage over Governor Janet Mills. The new poll from the Maine People’s Resource Center added to a series of recent surveys showing Platner ahead of Collins or within striking distance, as the state's June 9 primary draws closer. Collins, a five-