CREATE TABLE table_18198 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Status" CLOB, "Opponent" CLOB)

Who ran unsuccessfully against Bill Hefner?
SELECT "Opponent" FROM table_18198 WHERE "Incumbent" = 'Bill Hefner'
SELECT "Opponent" FROM "table_18198" WHERE "Incumbent" = 'Bill Hefner'