Ok I am not sure which is the more correct one:
"I like the person who cleaned up the apartment."
"I like the person whom cleaned up the apartment."
You voted for him.
He is the man for whom you decided to vote.
I am looking forward to hearing for whom you decided to vote.
I am looking forward to hearing whom you decided to vote for.
Whom is the object of the preposition "for."
Ok, would you go so far as to say that one cannot say?
"I am looking forward to hear..."