What Is Suggested by the Research of Howell and His

What is suggested by the research of Howell and his colleagues?

A) Local policy initiatives are a helpful way to understand the reach of presidential power during war.
B) The differences between proposed and enacted budgets provide a measure of presidential success that can be compared across policy domains.
C) The number of vetoes sustained by Congress during a time of war is key to assessing congressional support for the president.
D) Supporting statements issued by international organizations are an effective measure of presidential power during a time of war.