PORTLAND, Maine (AP) — Graham Platner has attracted a following of enthusiastic supporters and been confronted with a string of controversies as he has transformed from a political unknown into the leading Democratic candidate for U.S. Senate in one of the year’s most critical races.Platner is running in Tuesday’s primary for the chance to face longtime Republican Sen. Susan Collins, a contest that Democrats see as a must-win as the party tries to claim control of the Senate in November. Platner’s path to the nomination grew easier in late April when Democratic Gov. Janet Mills dropped out citing a lack...