What would summer be without some dusty English etymology: M-W's Word of the Day is demagogue, "a leader who makes use of popular prejudices and false claims and promises in order to gain power." But it wasn't always derogatory:

When the ancient Greeks used "demagogos" they meant someone good -- a leader who used outstanding oratorical skills to further the interests of the common people. Mid-17th-century writers such as Thomas Hobbes and John Dryden and, later, Jonathan Swift employed the English word that way. But at the same time the word -- from "demos," meaning "people" and "agein," which means to lead -- took a negative turn, coming to suggest one who uses his powers of persuasion to sway and mislead. "A plausible, insignificant word, in the mouth of an expert demagogue, is a dangerous and a dreadful weapon," declared Robert South, known for his sermons, in 1716. Thus when the verb "demagogue" appeared also around that time it had the negative twist of "behave like a demagogue."