CREATE TABLE table_26655 ("District" TEXT, "Vacator" TEXT, "Reason for Vacancy" TEXT, "Successor" TEXT, "Date of successors taking office" TEXT)

When rudolph kleberg (d) is the successor is the reason for vacancy?
SELECT "Reason for Vacancy" FROM table_26655 WHERE "Successor" = 'Rudolph Kleberg (D)'
SELECT "Reason for Vacancy" FROM "table_26655" WHERE "Successor" = 'Rudolph Kleberg (D)'