As he brags that he is turning down millions of dollars for his presidential campaign, Donald Trump has leveled a steady line of attack against his rivals: that they are too cozy with big-money super PACs and may be breaking the law by coordinating with them. “You know the nice part about me?” he told reporters in Iowa in August. “I don’t need anybody’s money.” What Trump doesn’t say is that he and his top campaign aide have connections to a super PAC collecting large checks to support his candidacy — a group viewed by people familiar with his campaign...