In discouraging efforts to promote him as an alternative Democratic nominee, Secretary of State Edmund Muskie said he "loved" his job and was committed to serving the Carter administration.

That, however, was before he was subjected to the same kind of White House brush-off that finally drove his predecessor, Cyrus Vance, into resigning. And before Vance, still another State Department chief, William Rogers, quit because President Nixon continually bypassed him.

If Muskie is wise, he will lose no time clarifying his position with President Carter. It will be downhill all the way for the present secretary if he, too, permits his authority and prestige to be. comprised. Better a showdown now than later.

Since Carter got all the worst of the publicity in the wake of the Vance resignation, it was assumed that the White House would treat his successor with kid gloves for fear of Muskie's notoriously short temper, but that is not the way it appears to be working out.

The president's decision to go ahead with the mission to rescue the hostages in Iran was made not only without Vance's approval but without his knowledge. The secretary was away from Washington when the green light was flashed.

Muskie now finds himself in a similar position. He, too, was out of Washington when he learned from newspaper headlines that Carter had just signed Presidential Directive 59 altering U.S. policy on fighting a nuclear war. Muskie was natually surprised and embarrassed when he read about it, as were the top officials of the government's Arms Control and Disarmament Agency, who also were excluded from consultation, even though the ACDA is, of course, concerned with the control of nuclear weapons.

Our bewildered allies are entitled to wonder how long this is to go on. It is, to put it mildly, disconcerting for our partners to discover at critical moments that the secretary of state is less than fully informed on American foreign policy. Still, that has been the case for over 10 years. Even Henry Kissinger found himself in an uncertain role as Gerald Fords's administration drew to a close.

The latest episode revolves around the problem of deterring nuclear war. Until now, the United States and Russia have relied on a "balance of terror" to keep the peace. Under this doctrine of "mutual assured destruction," any attack by one superpower on the other would trigger massive retaliation, primarily aimed at wiping out cities and most of the population.

Some years ago, however, James Schiesinger, then secretary of defense, began promoting an alternative strategy based on nuclear exchanges short of total nuclear war, the idea being to counter a "limited" Soviet strike with a limited response, concentrating on Russian military installations and war industry complexes.

The proposal was rejected as impractical and dangerous. How could a "prolonged, selective" nuclear war be fought without doomsday escalation? Before taking office, President Carter frankly said he did not think it was possible for the United States and Russia to fight a limited nuclear war. And in his State of the Union message last year, Carter described the existing U.S. deterrents as "overwhelming."

Yet now, out of the blue, the "limited" plan has been revived chiefly through the interest of national security adviser Zbigniew Brzezinski and Defense Secretary Harold Brown. The end result is the sudden emergency of Presidential Directive 59.

Brown's justification is that the new strategy will "enhance" deterrents. But critics find it difficult to understand how the threat of merely limited retaliation could deter Russia more effectively than the fear of total annihilation.

Jody Powell, the White House press secretary, says the bypassing of Muskie was "inadvertent" even though it has gone on secretly for months. Powell also made the startling statement that the State Department is not usually involved in nuclear strategy. That will certainly be news to Vance, who was sent to Moscow by Carter to launch his first strategic arms limitation proposal in March 1977. Also, it was Kissinger, as secretary, who guided Gerald Ford in getting SALT II under way in 1974.

One mystery that Powell has not explained is why the new strategy, after being mulled over for years, suddenly had to be formalized and publicized just before the Democratic National Convention. There is no known need for such haste or for acting on such a long-range proposal without a complete government review.

The suspicion naturally arises that Directive 59 is not so much a message to Moscow as a message to Ronald Reagan and the Republican platform drafters that two can play at the hard-line, anti-Soviet game. The Republicans also called for "clear capability to destroy military targets." Carter's directive seems to say, "anything they can do, we can do better."