Washington — The essentially political nature of US strategic nuclear doctrine and practice is being revealed all over Washington this week. President Reagan, as expected, endorsed the recommendations of the special bipartisan commission charged with finding a home for the controversial MX missile. In doing so, he implicitly recognized that some of his most basic preelection convictions about nuclear weapons and superpower relations will have to be altered by the practicalities of governing.
The chairman of that commission, retired Air Force Lt. Gen. Brent Scowcroft, conceded in the first of what will be numerous congressional appearances that his group's findings are heavily circumscribed by politics.
On Capitol Hill, lawmakers with reputations as Pentagon critics have accepted the necessity for building and perhaps deploying the MX, as outlined by the Scowcroft panel. They find the panel's recommendations less objectionable than the other possible alternatives. More hawkish legislators, many with concerned glances toward 1984 reelection campaigns and public sentiment moving sharply away from a big defense buildup, are leading the sharp questioning of MX.
Both ends of Pennsylvania Avenue are responding as well to the nuclear freeze movement, which recent polls show has strong public support. The House of Representatives resumes debate on the freeze resolution today (April 20).
Administration officials acknowledge the growing political cast to such seemingly arcane and theoretical subjects as the so-called window of vulnerability. The Scowcroft commission in essence said that that ''window'' (a period during which the Soviet Union would allegedly be able to threaten US strategic forces without this country's being able to respond in kind) is not as wide as candidate Ronald Reagan warned, nor need it be closed as quickly.
''Whether the United States is vulnerable depends on our ability to respond in its totality, and it depends on a political dimension that musn't be ignored, '' said a senior official. ''If indeed we were not able to make what is obviously a controversial decision (to deploy the MX), the political impact of that would have to make the window of vulnerability a far more formidable and far more important factor in our security.''
In its recent report to the President, the MX commission emphasized this same concern: ''What we have most to fear is that confusion and internal divisions - sometimes byproducts of the vigorous play of our free politics - will lead us to lose purpose, hope, and resolve.''
Administration officials are emphasizing the President's new realism and flexibility in substantially embracing what is being advertised as a nonpolitical compromise on MX.
''In creating the commission, the President clearly recognized that we could not proceed without a bipartisan consensus,'' a senior Defense Department official said. ''The President has yielded to their judgment. He has now endorsed a commission report that differs from his earlier recommendation to the Congress.''
Not far below the surface concord, however, considerable division remains between the administration and legislators. Common Cause president Fred Wertheimer said this week, ''The lines are now clearly drawn for Congress.''
In congressional testimony Monday, MX commission members acknowledged that - politics aside - the best basing mode for the missile probably would have been something like the deceptive ''race track'' system proposed by former President Carter but cast aside by President Reagan largely because of local opposition. Yet when Congress refused to accept the ''dense pack'' proposal put forth by the current administration, that left the commission very little room to maneuver.
It ultimately settled on placing the 100-ton MX in existing Minuteman missile silos (which Congress has already rejected), while adding two new factors designed to make it more palatable to lawmakers: development of a new, smaller, single-warhead mobile missile that would be less vulnerable, less threatening, and therefore less likely to upset the nuclear balance; and a new emphasis on arms control stressing equality of warheads rather than launchers.
This latter point presents a problem for the President's arms control proposal (START), which emphasizes launchers. Will the administration yield on this point as well as MX basing and small missile development?
Not much progress has been evident at the strategic arms talks in Geneva, and many key lawmakers tie their support for keeping MX alive to some evidence of administration sincerity in achieving true arms control.
Asked whether the administration would accept what in essence is MX commission criticism of the START proposal, a senior administration official said only, ''It will receive quite intensive scrutiny.''
It remains to be seen whether scrutiny alone will win a reprieve for the MX on Capitol Hill. Congress now has 45 days to accept or reject the commission's (now the President's) recommendations.