CREATE TABLE table_26657 ("District" TEXT, "Vacator" TEXT, "Reason for Vacancy" TEXT, "Successor" TEXT, "Date of successors taking office" TEXT)

When rudolph kleberg (d) is the successor what is the date of successors taking office?
SELECT "Date of successors taking office" FROM table_26657 WHERE "Successor" = 'Rudolph Kleberg (D)'
SELECT "Date of successors taking office" FROM "table_26657" WHERE "Successor" = 'Rudolph Kleberg (D)'