After some verbs the direct object can be followed by an object complement – a noun or adjective which describes or classifies the object.
- They elected him their leader.
- The other children called her stupid.
- We all regarded her as an expert.
- Queen Victoria considered him a genius.
When these clauses are made passive, these objects complements become subject complements; they come after the verb.
- He was elected their leader.
- She was called stupid by the other children.
- She was regarded as an expert.
- He was considered a genius by Queen Victoria.