THE press conference that President Reagan is scheduled to hold tonight may very well be the turning point of his presidency. Domestically, Mr. Reagan has achieved much of what he set out to do when he won office six years ago. The policies are in place, and even the loss of the Senate by the Republicans in this month's election will not seriously hamper his domestic agenda.
It is in foreign policy that Reagan has sought to bring final luster to his term. And ironically, it is in its approach to foreign policy that his administration is in greatest disarray. Whether he can recover remains to be seen.
His press conference will be critical insofar as the confidence of the American people in him is concerned. All the evidence is that even those who give him the benefit of the doubt about the honorable intention of his approach to Iran find the execution of the operation fuzzy, ill advised, and amateurish.
It will be an extraordinary historical coincidence if Iran, the issue that broke President Carter, leaves an irredeemable stain on President Reagan's record.
Iran is not the only foreign policy issue that has caused the Reagan administration grief in recent months.
There is the Reykjavik summit with the Soviet Union, into which the administration entered impulsively and ill prepared. The foreign policy professionals may at times overdo this need for preparation, but Reykjavik certainly underlined the dangers of letting two world leaders embark on summitry in the atmosphere of a freewheeling poker game.
Then there was the disinformation debacle arising from the administration's attempt to confuse Libya about United States intentions.
All the evidence is that the administration did adopt a policy designed to upset Libya and did not object to cutting corners with the foreign press, but did not adopt a policy to lie to the American press. The affair was so badly handled, however, that the Reagan administration's credibility was badly besmirched.
Then there was the Hasenfus affair, in which an American plane running weapons to the anti-Sandinist contras was shot down by the Nicaraguans with an array of incriminating documents aboard.
This was supposedly a private operation; the coordinating trail nevertheless led back to Lt. Col. Oliver North on the President's National Security Council staff.
What has gone wrong with the Reagan foreign policy team? Any analysis must necessarily focus on the leadership of the National Security Council staff, which has been downgraded in the Reagan administration.
Its current head, Vice-Adm. John M. Poindexter, is a bright naval officer, and his predecessor, Robert C. McFarlane, was a Marine Corps officer. Both are able technicians. Neither has the stature of a Henry Kissinger or a Zbigniew Brzezinski, who have previously held the post.
Of course, it must be said that other Cabinet secretaries, like the secretaries of state and defense, are not necessarily enthusiastic about having strong strategists in the national-security adviser's role. They prefer policy coordinators who can be worked with, rather than policy innovators who sometimes obstruct others' initiatives.
But the Reagan administration, after downgrading the quality of the NSC staff, seems to have compounded the problem by giving this staff an activist and operational role, cutting out the departments that are more skilled in foreign affairs.
Thus it has gotten into deep trouble.
Tonight's press conference will be a test of Mr. Reagan's personal credibility with the American people.
But beyond that there will need to be some rethinking, and perhaps restructuring, of the administration's foreign policy apparatus.
Whether there will be changes at the NSC staff remains to be seen, but a new definition of the staff's role seems in order.
Secretary of State George Shultz is clearly at odds with administration actions toward Iran, and whether he will be around for two more years must also be a question mark.
Secretary of Defense Caspar Weinberger also disapproved of the weapons-to-Iran caper. He is probably battle-weary after years of the long days and pressures imposed on our top officials; his longevity in office may also be a matter for conjecture.
The decisions the President makes in the next few weeks may thus decide whether his handling of foreign policy has left a sheen or a shadow on his presidential record.