The correct answer is:
Political novelist
Explanation:
Robert Penn Warren was an American novelist, poet, critic and teacher. Warren is known for being one of the founders of the literary analysis named the New Criticism and for winning three Pulitzer Prices, one for fiction and two for poetry. His must known work is about corruption in politics, named All the King's Men, therefor, the category Robert Penn Warren fits best is political novelist, although he did several romantic poems his political works had more impact.
