CREATE TABLE table_18581 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

what's the district with result being re-elected and candidates being clarence f. lea (d) unopposed
SELECT "District" FROM table_18581 WHERE "Result" = 'Re-elected' AND "Candidates" = 'Clarence F. Lea (D) Unopposed'
SELECT "District" FROM "table_18581" WHERE "Candidates" = 'Clarence F. Lea (D) Unopposed' AND "Result" = 'Re-elected'