It’s official: Republican Sen. Susan Collins will face Democrat Graham Platner this fall, NBC News projects, in what will be a marquee election in the fight for control of the Senate. Collins and Platner both won their primaries on Tuesday, in a predictable result. Collins, first elected to the Senate in 1996, ran unopposed for re-nomination as she seeks a sixth six-year term. And Platner, a veteran and oyster farmer running in his first political race, faced little Democratic competition as