At least six Maine Democrats had jumped in to fill the sudden void ?on ?Thursday in a critical U.S. Senate race after progressive candidate Graham Platner dropped out when a string of controversies culminated this week with an accusation of rape.The seat in the rural northeastern state, currently held by Republican U.S. Senator Susan Collins, is vital for the party's chances of taking control of the Senate in November's midterm elections. Six Democratic candidates have formally announced their campaigns in ?the hours since Platner dropped out less than three weeks before the ballot deadline. Two of them came up short...