CREATE TABLE table_689 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Status" TEXT, "Opponent" TEXT)

what's the party with opponent being mike oxley (r) unopposed
SELECT "Party" FROM table_689 WHERE "Opponent" = 'Mike Oxley (R) unopposed'
SELECT "Party" FROM "table_689" WHERE "Opponent" = 'Mike Oxley (R) unopposed'