Chump song meaning

The narrator in this song expresses his hatred towards some unidentified person. He doesn't explain why exactly he hates them, he just states that they are the reason of his misery because apparently they did something that makes the narrator mad.

There is a legend that Armstrong wrote this song about a boyfriend of a girl he fancied, and even though he’s never actually met that person, he had a reason to hate them. If the legend has its truth then it would explain certain parts of the lyrics, such as “maybe it’s just jealousy…” or “you still got one over on me” - obviously, the author was jealous of the guy who dated the girl he liked and that apparently was a good enough reason for Armstrong to start hating the “chump".