CREATE TABLE table_18630 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

William Fadjo Cravens is the only candidate who was first elected in 1939.
SELECT COUNT("First elected") FROM table_18630 WHERE "Incumbent" = 'William Fadjo Cravens'
SELECT COUNT("First elected") FROM "table_18630" WHERE "Incumbent" = 'William Fadjo Cravens'