CREATE TABLE table_25100 ("District" CLOB, "Vacator" CLOB, "Reason for change" CLOB, "Successor" CLOB, "Date successor seated" CLOB)

Name the successor for not filled this congress
SELECT "Successor" FROM table_25100 WHERE "Date successor seated" = 'Not filled this congress'
SELECT "Successor" FROM "table_25100" WHERE "Date successor seated" = 'Not filled this congress'