Troy Jackson picked to challenge Collins in Maine after Platner's exit

Democrats selected former Maine Senate President Troy Jackson on Saturday to challenge Republican Sen. Susan Collins this fall after Graham Platner's embattled campaign ended. Why it matters: Jackson's selection is another win for the left flank of the Democratic party, which lined up behind another progressive candidate as their best shot at flipping one of the most important seats to win back Senate control. Driving the news: Delegates to a special nominating convention selected Jackson…