CREATE TABLE table_18702 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

what's the district with candidates being john e. rankin (d) unopposed
SELECT "District" FROM table_18702 WHERE "Candidates" = 'John E. Rankin (D) Unopposed'
SELECT "District" FROM "table_18702" WHERE "Candidates" = 'John E. Rankin (D) Unopposed'