To understand the effect of the nuclear freeze movement on politics and on policy--why it is likely to have less direct effect on politics and perhaps more on policy than one might think--you have first to try to understand why nuclear weapons policy has excited so much concern just now.

The answer is not immediately obvious. Nuclear weapons strategists point out that the United States and the Soviet Union have had nuclear weapons for 33 years, and none has been fired in anger in that time. Peace between the superpowers has been maintained for longer than in any other period in our lifetimes. Our system of nuclear deterrence, while dangerous, seems stable. Why are so many people talking as if they had just discovered nuclear weapons?

The political analyst has a ready answer: Ronald Reagan. A great many Americans and Europeans believe that Reagan is significantly more likely than his predecessors to get us into a nuclear war. These beliefs come both from the assertive tone of the administration's foreign policy and from careless statements by the president and his high advisers--talk of tactical nuclear war, disputes about nuclear warning shots, discussions of the neutron bomb, fumbling answers at presidential press conferences. Before Reagan was elected, there were no massive peace marches in Europe, no nuclear freeze resolutions in town meetings in Vermont.

The emergence of a simple, comprehensible proposal like the freeze is a nice windfall for the Democrats (freeze proponents like to point out that they have Republican backers, too, but they don't have all that many). Simplicity is the natural weapon of the party out of power, and leading Democrats, fresh from being savaged by what they consider simplistic attacks on the Panama Canal and SALT II treaties, are happy to embrace the freeze. The same Democrats who endorse the proposal now did not advance it when they held office, just as Republicans once out of office attacked the canal treaties and arms control agreements their party's administration had been moving toward.

Yet the freeze is not likely to be a direct issue in very many 1982 elections. It will be on the ballot in California and other states; as much as one-quarter of the electorate might have a chance to vote on it. Probably that vote will be favorable. Initial polls-- and the likelihood that there will be no well-organized opposition--suggest the referenda will pass. But for that very reason the freeze is unlikely to be an issue in congressional races. Both Democrats and Republicans in the least hawkish parts of the country--the northern tier from New England through the upper Midwest to the Pacific Northwest and California--will try to sound friendly to the freeze. Politicians in the most hawkish part of the country, the South, will ignore it. Barring unexpectedly massive gains for the Democrats, the 1982 elections by themselves will not substantially add to the minorities in the Senate (25) and House (168) who now support the freeze resolutions.

But there will probably be, perhaps already has been, an effect on public policy, for the same reason the freeze issue has struck such a chord: too many people are too scared that Ronald Reagan will pull the nuclear trigger. In those circumstances, it is not enough for the administration to resort to the natural response of the party in power and plead that the world is complex and that there are no easy solutions. Jimmy Carter tried that in 1980, with predictable results: voters do not like to be told that they are too dumb to understand things.

Instead, Ronald Reagan, as long as he is president, will be under pressure to reassure people over and over again that he is not unduly risking nuclear war. He will have to emphasize disarmament efforts, even if they do not lead in the directions he wants; he will have to avoid commitments of American military troops to conflicts abroad, even if he wants to fight.

Presidents seem forced to overcompensate on foreign policy: peace candidate Johnson went to war and anti-communist Nixon went to China. The freeze proposal articulates grave reservations many people have about Ronald Reagan. It will be in his continuing political interest to allay these fears and sound like a peace president, whatever his own instincts and preferences.

The writer is a member of the editorial page staff. if he wants to fight.

Presidents seem forced to overcompensate on foreign policy: peace candidate Johnson went to war and anti-communist Nixon went to China. The freeze proposal articulates grave reservations many people have about Ronald Reagan. It will be in his continuing political interest to allay these fears and sound like a peace president, whatever his own instincts and preferences.