CREATE TABLE table_66238 ("State  ( class ) " TEXT, "Vacator" TEXT, "Reason for change" TEXT, "Successor" TEXT, "Date of successor's formal installation" TEXT)

Which State (class) has a Successor of harry f. byrd, jr. (d)? Question
SELECT "State (class)" FROM table_66238 WHERE "Successor" = 'harry f. byrd, jr. (d)'
SELECT "State (class)" FROM "table_66238" WHERE "Successor" = 'harry f. byrd, jr. (d)'