Oyster farmer Graham Platner has a wide lead over Gov. Janet Mills in the Maine Democratic primary election for the U.S. Senate, according to a new poll. The race may be critical as Democrats try to take back control of the Senate, where Republicans hold a narrow 53-47 majority. The poll, conducted by Emerson College, also shows that in a hypothetical general election, both Platner and Mills have an advantage over incumbent Republican Sen. Susan Collins. Platner, a 41-year-old former Marine and combat veteran, is one of many younger Democrats nationwide looking to upstage older candidates. According to the poll,...