The three-year-long investigation into Comptroller John C. Liu’s campaign finances has brought down two of his former staffers, but it has never touched him, and at a mayoral candidates’ forum on Thursday he let everyone know how tired he was of being investigated: “Three years of investigating. They wiretapped my phones for 18 months. They reviewed a million documents and messages. They interrogated thousands of my supporters. And yet, what do they have to show for it? It’s time to put up or shut up already.” That does sound awfully unpleasant.