When former Milwaukee Sheriff David Clarke intimated in early 2017 that he would be joining Donald Trump's nascent administration, CNN obtained a copy of Clarke's master's thesis from the Naval Postgraduate School and revealed that Clarke had copied blocks of text from other sources. The borrowed passages, as CNN noted, had footnotes identifying their sources, but they failed to "indicate with quotation marks that he is taking the words verbatim." Few responses to CNN's revelation encapsulated the giddiness of the academic left more than that of Kevin M. Kruse, a Princeton historian and rising social media star. When the Clarke...