CREATE TABLE table_2159547_3 (reason_for_change VARCHAR, vacator VARCHAR)

Why did Robert L. Bacon (r) vacate?
SELECT reason_for_change FROM table_2159547_3 WHERE vacator = "Robert L. Bacon (R)"
SELECT "reason_for_change" FROM "table_2159547_3" WHERE "Robert L. Bacon (R)" = "vacator"