What Does Aaron Wildavsky Mean When He Refers to "Two

What does Aaron Wildavsky mean when he refers to "two presidencies?"

A) There are so many responsibilities that the presidency should be split into two offices.
B) There is a difference between "Head of Government" and "Head of State."
C) The role of the Vice President is so important that it could be a "second president."
D) The President has considerably more power in domestic policy than in foreign policy.
E) The President has considerably more power in foreign policy than in domestic policy.