DEMOSTHENES: A demagogue must be neither an educated nor an honest man; he has to be an ignoramus and a rogue.

Aristophanes (c. 450-c. 388 BC) Athenian comedic playwright

The Knights, ll. 191-3 [tr. O’Neill (1938)]
    (Source)

Alt. trans. "For the character of popular leader no longer belongs to a man of education, nor yet to one good in his morals, but to the ignorant and abominable." [tr. Hickie (1853)]