THE net effect of the joint congressional committee hearings into the Iran-contra affair can be summed up as follows: For the balance of the Reagan administration, with a possible carryover into the next two or three administrations thereafter:
1.The Central Intelligence Agency will be more professional and less political.
2.The size of the staff of the National Security Council will be smaller, and it will avoid running covert operations out of the White House basement.
3.The president will listen more carefully to the advice of his senior Cabinet officers.
4.The White House will hesitate before plunging into another foreign policy venture opposed by a majority in the Congress.
5.And political science majors in universities around the United States will study the affair as one more case in the continuing evolution of the relationship between the Congress and the president.
All of this adds up, of course, to the fact that the disclosure of the secret talks with Iran and the diversion of profits to the contras (most of which never reached them) have left the present President hemmed in by professional advisers who will never allow him to take many more, if any, bold or radical ventures in either foreign or domestic policy.
The old days of ``letting Reagan be Reagan'' are over.
Opinion will differ over how much his power of initiative has been curbed. Conservative political analyst Kevin Phillips, writing in the Washington Post, thinks that Mr. Reagan's presidency ``is in danger of fading beyond lame-duckhood to what verges on irrelevance.''
That may be putting it a bit too strongly, but when Mr. Reagan now makes one of his rhetorical pronouncements on television, I notice a tendency in the audience to pay slight or no attention. It's almost as though what he says doesn't really matter anymore.
Back when Nikita Khrushchev was toppled in Moscow, we were told that the Soviet Union would henceforth be run by ``collective leadership.'' It was not. Leonid Brezhnev soon emerged as the new top man. The Soviet system seems to require a czar at the top.
The US system is more flexible. It allows a strong president to be almost a czar, but on one condition. He must have majority support in the Congress. Abraham Lincoln and Franklin D. Roosevelt were powerful Presidents who by and large did what they wanted to do, but usually only after being sure they could carry a majority in the Congress.
No American President, not even Andrew Jackson, has been able to behave like a czar unless he could mobilize that essential majority in the Congress.
That, of course, is the main lesson of the Iran-contra affair. The present President attempted to put through a policy that had been expressly forbidden by the Congress. He raised funds for the contras by private and extraconstitutional methods (sale of guns to Iran, solicitations to Saudi Arabia, Bahrain, etc.), and he waged war (mining harbors and funding contras) without consent of the Congress.
The present President ends up surrounded by new advisers and aides at the White House (Howard Baker, Frank Carlucci) and a new man at the CIA (Judge Webster) who have, in effect, been picked for the job by the Congress. This is not literally true. But they were picked only after quiet, back-stairs consultation with the leaders of the Congress. The appointments were of men in whom the Congress has confidence. They are nonpartisan professionals.
As a result we now have something approaching a collective leadership in Washington. Mr. Reagan still sits at the head of the conference table, and due deference is paid to his wishes. He was perhaps decisive in the decision to go ahead with the ``flagging'' of the tankers in the Gulf. That operation has the ``Reagan touch.'' The alternative was to talk to the Soviets and make a joint approach with the Soviets to Iran to try to end the Iran-Iraq war.
But the Reagan presidency will never again be what it was before Mr. Reagan agreed to the secret arms-for-hostages deal.