CREATE TABLE table_681 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Results" TEXT, "Candidates" TEXT)

When was the incumbent Sherrod Brown first elected?
SELECT MAX("First elected") FROM table_681 WHERE "Incumbent" = 'Sherrod Brown'
SELECT MAX("First elected") FROM "table_681" WHERE "Incumbent" = 'Sherrod Brown'