A Liar Speaks Nothing But The Truth

Three people are being interviewed to see if they can get a job at Hell Corporation. Out of the three people, only one person can get the job.

Interviewer: Why do you guys deserve to be here?

Banker: I am a thief, sir! I cheat, scam and steal whenever I can!

Politician: I am an idiot, sir! I declared war on my ally!

Teacher: I am a propagandist, sir! I always tell my students lies!

Interviewer: Which one of you guys is a liar?

Banker: The stupid politician is a liar.

Politician: The cheating banker is a liar.

Teacher : Both the banker and the politician are liars.

Given these statements, who is the real liar?