CREATE TABLE table_18584 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Result" CLOB, "Candidates" CLOB)

who is the the incumbent with candidates being jack z. anderson (r) unopposed
SELECT "Incumbent" FROM table_18584 WHERE "Candidates" = 'Jack Z. Anderson (R) Unopposed'
SELECT "Incumbent" FROM "table_18584" WHERE "Candidates" = 'Jack Z. Anderson (R) Unopposed'