Responding to several people generally.
Look at the recent history of the term “witch hunt.” Starting with Google ngrams, I searched hits it gave from 2000-2017, in which the term appears predominantly in books about Salem or other historical witches. The few modern examples include the Catholic priesthood, accusations of satanic preying on children, and McCarthyism.
In 2018, though, you start seeing overtly political, usually but not always right-wing, books on the list. The Russia Hoax: The Illicit Scheme to Clear Hillary Clinton and Frame Donald Trump. Secret Empires: How the American Political Class Hides Corruption and Enriches Family and Friends. The Deep State: How an Army of Bureaucrats Protected Barack Obama and Is Working to Destroy the Trump Agenda. Witch Hunt Or Justice?: Accusations Against Public Figures. Witch Hunt: The Story of the Greatest Mass Delusion in American Political History. Exonerated: The Failed Takedown of President Donald Trump by the Swamp. Power Grab: The Liberal Scheme to Undermine Trump, the GOP, and Our Republic. Radicals, Resistance, and Revenge: The Left’s Plot to Remake America. Triggered: How the Left Thrives on Hate and Wants to Silence Us. Silent No More: How I Became a Political Prisoner of Mueller’s “Witch Hunt”.
Any dictionary editor would look at this sudden profusion and start writing a new secondary meaning for the term. The earlier uses, even for the McCarthy era, were not overtly political. These are or are examining the new political usage. It’s impossible to keep Trump out of this; nothing can be more obvious that his constant use of the term to apply to his proclaimed innocence from crimes is driving the similar use of the term by others on the right. The personalized titles also show that the term is being used by aggrieved individuals, not just a class of persons. This is new, and interesting, and distinct from earlier usages even if it manifestly is descended from them.
It’s a perfect capsulized version of how dictionaries update themselves that will probably go into every future book on dictionaries. It’s only prescriptivism when you remember that prescriptivism and modern dictionary definitions are synonymous.
As a footnote, “fake news” hardly appears at all in ngrams before 2014. Then it zooms upward. But in 2007, Howard Kurtz’s book on the turmoil on the evening network news shows, Reality Show, had a chapter titled “Fake News.” It was all about Jon Stewart and The Daily Show. Obviously, then, fake news meant satirical or comic takes on the news rather than the current meaning of any real news that makes us look bad. That’s a huge flip, far larger than the nuances of “witch hunt.”