President Reagan may not have lost control of foreign policy, but he has lost control of the foreign policy debate.

He is not leading the conversation on his two major preoccupations, Central America and nuclear disarmament.

The Democrats, for instance, in the wake of his joint address to Congress, should be cowering at his not-so-veiled threat to charge them with "losing" El Salvador if they fail to answer his call for "bipartisan action."

Many are nervous, but they are all the same going ahead with their plans to end his not-so-secret war against Nicaragua.

The first witness for a bill sponsored by Reps. Edward P. Boland (D-Mass.) and Clement J. Zablocki (D-Wis.), which would wind down the U.S. operation to overthrow the government in Managua--a goal the president denied in his majestic address, but acknowledged in an interview with White House reporters--will be Majority Leader James C. Wright Jr. (D-Tex.), who, paradoxically, supports the president on El Salvador.

Luckily for Reagan, the Democrats have not focused on a true bipartisan solution to the problem: the recommendations of the Linowitz Commission.

The commission had heavy Republican representation, including two veterans of the Nixon administration, Elliot L. Richardson and Frank Shakespeare, David Rockefeller and even former chairman of the Joint Chiefs of Staff, Gen. David C. Jones--all of whom signed a plan for multilateral negotiations that would include Cuba and the Soviet Union.

The president's conservative supporters are not talking, as they should be, about his splendid oratorical stand against the communist hordes poised to take over the region. His denial of any resemblance to Vietnam displeased them.

To them, it is Vietnam--and a chance to refight a losing battle against the Red Tide. As for not overthrowing the Nicaraguan government, the thunder from the right is: if not, why not? To them, Nicaragua is another Cuba, a peddler of revolution, a demon player of dominoes.

Of all those not following the president's script, the Roman Catholic hierarchy may be the most disappointing. They should, by his lights, be singing hosannas to him for espousing tuition tax-credits and opposing abortion.

But they have veered off into a cosmic "pro-life" movement. The stiffened, final version of their pastoral letter on nuclear war was an affirmation that the preservation of the planet is more important than the preservation of the parochial school.

There was, of course, a time when an American president could take for granted Catholic support for any foreign policy venture aimed at godless communism. The leaders of an immigrant church wanted to be counted with those whose Americanism was above question.

No one personifies how far they have come more than Cardinal John Krol of Philadelphia, who in the 1970s participated in President Nixon's famous "Sunday Worship Services" during the Vietnam war.

Cardinal Krol, at a news conference at Trinity College held in before an ecumenical worship service to celebrate the pastoral letter, was quoting the Rev. Martin Luther King Jr. and Mohandas Gandhi.

Scientists, by Reagan's lights, are doing no better by him.

In his "Star Wars" speech he called upon the scientific community "who gave us nuclear weapons" to help him build an outer-space defense against them. Instead of responding to the challenge, they are telling him to pack it in.

Next week, Hans Bethe, project director at the Los Alamos National Laboratory and one of the repentant bomb-makers who has joined the Union of Concerned Scientists, will testify before a Senate committee against Reagan's "dream" of a laser-beam shield. To oppose the Nobel Prize winner, the administration is sending in Kenneth L. Adelman, whom the Senate dubiously confirmed last month as director of the Arms Control and Disarmament Agency.

And finally to the list of those who are not speaking their expected lines must be added U.S. doctors. Once they could be depended on not to take stands on social issues. Now, these privileged haves of our society are down in the arena, mobilizing against the arms race.

Dr. John Pastore of Tufts University, a distinguished cardiologist, and a member of the International Physicians for the Prevention of Nuclear War, came to Washington to speak to the Women's Democratic Club about the need to enlist in the cause of peace.

He spent two years in Hiroshima as a member of the casualty commission. He participated in an unprecedented telecast with Soviet doctors about the horror and folly of nuclear war. He is going to Amsterdam to negotiate with the Soviets for another joint venture, this one about the effect of the nuclear threat on the children of the world.

He is another example of those who are making it difficult for Reagan to manage the dialogue on foreign policy.