Limbaugh has explained his pronunciation of Reverend Jackson as an imitation of how William F. Buckley did it.
Exactly correct. I recall the show when Rush gave the explanation. W.F. Buckley was interviewing the good Reverand and was cuffing him around intellectually. Calling him “Reverand JACK ssss on” in his east coast, hoi poloi, diction. I was hysterical to listen to Rush explain it.