Demagogue

Demagogue \DEM-uh-gog\ , noun;
1. A leader who obtains power by means of impassioned appeals to the emotions and prejudices of the populace
2. A leader of the common people in ancient times

This word dates to the 1640's and comes from Greek demagogos ("popular leader" or "leader of the mob"), possibly with the influence of French demagogue. It comes form a combination of demos + agogos ("people" + "leader"). Agogos derives from agein, which means "to lead" and is the forebear of act. The Greek word dates back to Athens in the 5th century B.C.E. and has had a sense of disparagement since that time. There is a verb form of demagogue in American English that was first attested in 1964.

Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Sunday, March 6
Etymologies come from the Oxford English Dictionary and/or Etymonline.com