Why Did Trey Gowdy Stop the Movement to Impeach Rod Rosenstein?

Mark Levin says that Gowdy ignored many sound reasons for Rosenstein's impeachment - and sees his performance in this matter as a repeat of Gowdy's "go-nowhere" treatment of the Benghazi investigation, which he also chaired. [The unspoken question has arisen about Gowdy being a 'mole' among conservatives acting to appear to be a champion of reform but actually working to prevent it.] [...]