ON THE CAMPUSES, in the scientific community and among "peace groups," a national movement is coalescing around the theme that there is now a growing threat of nuclear war. The movement's dimensions appear modest at the moment, but its membership is active, elite and articulate, and already some national politicians are paying it heed. In a country with a notoriously short political attention span, it is a strong candidate to become this year's vogue.

In a sense, this movement represents a continuation of the 1980 political campaign--by the losers--by guerrilla means. The participants favor policies associated, sometimes a bit inaccurately, with Jimmy Carter, or at least with the early Jimmy Carter: limiting the nuclear-arms buildup, negotiating restraints on strategic weapons, trying to limit the spread of nuclear arms and raising the nuclear threshold in war planning. Ronald Reagan is associated, sometimes a bit inaccurately, with contrary policies, and he is the target of many of the movement's alarms.

It would be wrong, however, to regard the movement simply as the Democratic left in disguise. To ask whether the actual threat of nuclear war is growing introduces a series of debates that we shall sidestep here. But there is in the country a palpable and measurable increase in the level of anxiety about nuclear war. It arises basically from the collapse of the grand d,etente experiment of the 1960s and 1970s: the promise of superpower restraint in both political competition and arms-building competition has not been adequately borne out. In such circumstances, concern about the threat of war, far from appearing farfetched or "emotional," takes on a certain prudent edge.

There is, nonetheless, an off-putting note in the tone of too much of the discourse coming out of the nuclear-protest movement. It expresses itself in assumptions, and sometimes in explicit allegations, that President Reagan is little more than a nuclear simpleton. This is, of course, nonsense. His policies can be criticized; we have criticized some of them, and will no doubt continue to do so. But it is no fairer to look on Mr. Reagan as a warmonger than it is to look on the mainstream of the new movement as appeasers. What the protesters can properly call on him to do is to demonstrate a more convincing awareness of the dangers of nuclear war. What he can ask of them is to address what seems to be the central element, not very well articulated, in his own nuclear thinking: the fear that the old familiar mutual deterrence is not safe to rely on any more.

The nuclear movement could yet gain a hearing for a wider range of ideas than are a part of the current official consensus. This is too valuable and necessary an undertaking to spoil by going shrill.