CREATE TABLE table_23085 ("District" TEXT, "Vacator" TEXT, "Reason for change" TEXT, "Successor" TEXT, "Date successor seated" TEXT)

Name the successor for pennsylvania 15th
SELECT "Successor" FROM table_23085 WHERE "District" = 'Pennsylvania 15th'
SELECT "Successor" FROM "table_23085" WHERE "District" = 'Pennsylvania 15th'