demagogue

1. A political leader who seeks support by appealing to popular desires and prejudices rather than by using rational argument.
2. (in ancient Greece and Rome) A leader or orator who espoused the cause of the common people

surreptitious

1 : done, made, or acquired by stealth : clandestine
2 : acting or doing something clandestinely : stealthy, a surreptitious glance

bloviate

–verb (used without object), ‐at·ed, ‐at·ing.
to speak pompously.

—Related forms
blo·vi·a·tion, noun