Relations between Congress and the executive branch have always been an uneasy mixture of mutuality and autonomy, cooperation and conflict. The Constitution required that the two branches of the federal government work in concert, but it also mandated a separation of powers—or what perhaps more accurately has been described as "separated institutions sharing powers." Inevitably, this situation has led to a clash of wills and a contest for power. In itself, this clash has not been a bad thing. It has been what the framers of the Constitution intended in order to preclude the exercise of arbitrary power and the tyranny of an overly centralized government.