CREATE TABLE table_1341690_18 (first_elected NUMBER, candidates VARCHAR2)

What year was Otto Passman (d) unopposed first elected?
SELECT MAX(first_elected) FROM table_1341690_18 WHERE candidates = "Otto Passman (D) Unopposed"
SELECT MAX("first_elected") FROM "table_1341690_18" WHERE "Otto Passman (D) Unopposed" = "candidates"