demagogue
definition
a political leader who seeks support by appealing to popular desires and prejudices rather than by using rational argument
example
The politician became a demagogue, winning votes by promising things he knew he could not deliver.
synonyms
rabble-rouseragitatorfirebrand
word origin — From Greek 'dēmagōgos', meaning 'popular leader', from 'dēmos' (people) + 'agōgos' (leader)