McFarlane quits post as national-security adviser to Reagan. His successor, Vice-Admiral Poindexter, provides continuity

For the third time in his administration President Reagan is changing his national-security adviser. The resignation of Robert C. McFarlane comes at a time when the President's foreign policy agenda is on the ascendant.

A key question now is whether Mr. McFarlane's successor, his former deputy, Vice-Admiral John M. Poindexter, will be as deft at dealing with the deep disagreements within the administration so the President can make the decisions necessary to move forward on arms control and other issues.

Diplomatic and political experts suggest that the McFarlane resignation points to:

The strong management style of White House chief of staff Donald T. Regan, who insists on centralized access to the President. White House officials say continuing friction between the national-security adviser and the chief of staff is a factor in McFarlane's decision to leave, though not the only factor. Yesterday, McFarlane termed this ``nonsense.''

The growing authority of Secretary of State George P. Shultz, who has managed to consolidate his own position and make the State Department more of a center of foreign-policy making than it was in the early years of the administration. Poindexter is not expected to challenge Shultz's status.

McFarlane is also known to be feeling the strain of five years at the White House and to have intended to leave his post before the end of Reagan's presidential term in any case. ``This place not only absorbs but drains a person,'' says a White House aide. ``It's extremely demanding and takes a lot from people's personal lives. That is an important factor in the decision.''

McFarlane is credited with developing a good relationship with the secretary of state, running interference in feuds between Mr. Shultz and Defense Secretary Caspar W. Weinberger, and articulating foreign policy options for the President. Given the competing interests of various departments and agencies within the government, the job of national-security adviser has grown increasingly important for coordinating policy.

``As we have moved into a more complicated world with strategic and economic concerns, it was inevitable that the President would want someone close to him to help coordinate the process,'' says David D. Newsom, director of Georgetown University's Institute for the Study of Diplomacy. ``And it has worked well when the national-security adviser has not set out to be a separate public and diplomatic personality.''

Initially, McFarlane, a retired Marine lieutenant colonel, maintained a very low-key posture as head of the National Security Council (NSC) staff. But gradually he emerged as a strong, if bland, voice in foreign policy. He took firm charge of managing diplomatic crises -- including the TWA hijacking. He met frequently with the press, and he moved out front in publicly articulating foreign policy issues.

With his successful management of the US-Soviet summit in Geneva, McFarlane reached the height of his NSC tenureship and gained considerable stature.

But he fought to keep his independence and not be absorbed by the White House chief of staff. Mr. Regan has a hierarchical style. He keeps tight control of the White House staff and has conspicuously moved himself to the fore, making sure he knows everything that is going on. President Reagan, who favors the Cabinet system, is comfortable with this style of management.

Political analysts observe that compared with, say, the administrations of Presidents Carter, Ford, and Nixon, the Reagan White House does not have a highly centralized policymaking apparatus.

``Except for the chief of staff, power does not center at the White House but in the departments,'' says Paul C. Light of the National Academy of Public Administration. ``Regan is doing what his position and mandate from the President require -- consolidating power and his access to the Oval Office. He's making sure that the director of the OMB [Office of Management and Budget] and the domestic and foreign policy advisers are subordinate.''

According to administration sources, ``Bud'' McFarlane and Regan were not close personally and clashed over a number of issues.

For Shultz, it has been useful to have an ally at the White House. He and McFarlane worked out an alliance on many key issues, including arms control. The appoiontment of McFarlane's deputy to succeed him suggests that this sort of relationship can be maintained.

Poindexter was the head of his class and brigade commander at the US Naval Academy -- an achievement President Reagan said Wednesday had seldom been matched.