CREATE TABLE table_18594 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

What is the first electedfor district ohio 18
SELECT "First elected" FROM table_18594 WHERE "District" = 'Ohio 18'
SELECT "First elected" FROM "table_18594" WHERE "District" = 'Ohio 18'