CREATE TABLE table_18204 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Status" CLOB, "Opponent" CLOB)

Who are the opponents in Massachusetts5 district?
SELECT "Opponent" FROM table_18204 WHERE "District" = 'Massachusetts5'
SELECT "Opponent" FROM "table_18204" WHERE "District" = 'Massachusetts5'