Wrong. She was the teacher whom we thought had seen us.
Right. She was the teacher who we thought had seen us.
Revise. He whom everybody thought would win the prize came out second.
302. Use the nominative forms who, whoever for the subject of a subordinate clause, even if a verb or a preposition immediately precedes who, whoever.
Wrong. I shall believe whomever has the best argument.
Right. I shall believe whoever has the best argument.
Wrong. A reward was offered to whomever returned the lost book.
Right. A reward was offered to whoever returned the lost book.
Revise. The decision as to whom should be punished no longer rests with me.