The vacator was james p. buchanan (d) and the successor was seated april 10th, 1937.
[['Lyndon B. Johnson (D)', 'DATE_SUCCESSOR_SEATED', 'April 10, 1937'], ['Texas 10th', 'VACATOR', 'James P. Buchanan (D)'], ['Texas 10th', 'SUCCESSOR', 'Lyndon B. Johnson (D)']]