President Reagan's expected appointment of William P. Clark to be his national security adviser would have seemed unthinkable a year ago.
Today the appointment of Deputy Secretary of State Clark, a man relatively inexperienced until recently in foreign affairs, appears from a Washington viewpoint to be the most logical of choices.
This is largely because Mr. Clark has proved himself at the State Department to be an effective mediator of bureaucratic disputes and coordinator of options and paper work -- a role similar in some ways to the one he would play as National Security Council (NSC) adviser. He also is a well-liked ''team player, '' in the words of some officials, and a close friend of Mr. Reagan's.
Richard V. Allen, the current national security adviser, took a leave of absence several weeks ago pending completion of investigations into his conduct while in that position. The Justice Department has cleared Mr. Allen of any criminal wrongdoing for accepting from a Japanese magazine a $1,000 honorarium -- which he left in his office safe -- and for accepting two gift watches from Japanese friends. But an internal White House review of Allen's conduct is continuing.
The controversy over Allen helped intensify a review of the White House foreign policy machinery -- a review apparently begun prior to Allen's leave. There have been complaints from within the bureaucracy that Allen was ineffective in coordinating foreign policy. More often than not, however, observers simply said that Allen and his NSC staff rarely counted for anything one way or the other in fashioning foreign policy. Allen's direct access to the President was reduced. White House counselor Edwin Meese III became the White House official, aside from the President, who dealt most authoritatively with foreign policy.
But perhaps in part because of inexperience in foreign affairs and because activities demanded so much of him, Mr. Meese did not appear to fill the lead role adequately. Vice-President George Bush, Reagan's crisis manager, took the lead in a number of policy-making meetings on Poland. But a feeling spread throughout the White House and the rest of the bureaucracy that the system must be revamped.