CREATE TABLE table_18667 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

who is the the incumbent with candidates being ben cravens (d) unopposed
SELECT "Incumbent" FROM table_18667 WHERE "Candidates" = 'Ben Cravens (D) Unopposed'
SELECT "Incumbent" FROM "table_18667" WHERE "Candidates" = 'Ben Cravens (D) Unopposed'