“Voter disgust over an avalanche of political spending by corporations, labor unions and other special-interest groups is driving support for a possible ban on ‘dark money’ in Montana, which could test a landmark Supreme Court decision,” the New York Times reports.“The ballot measure has strong backers from across the political spectrum, including a well-known former Republican governor and Democratic senator who have campaigned for it together.”“The main challenge: Threading the needle of Citizens United, the 2010 Supreme Court decision in which a 5-4 majority ruled that independent political spending by corporations and labor unions was a protected form of free speech.”