CREATE TABLE table_18345 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Result" CLOB, "Candidates" CLOB)

What year was Otto Passman (d) unopposed first elected?
SELECT MAX("First elected") FROM table_18345 WHERE "Candidates" = 'Otto Passman (D) Unopposed'
SELECT MAX("First elected") FROM "table_18345" WHERE "Candidates" = 'Otto Passman (D) Unopposed'