Boston — After a heady groundswell of public support in 1983, the antinuclear movement in the United States is now looking for a new surge of momentum. Yet even as antinuclearists struggle with the question 'What next?' the movement also must cope with the demoralizing effect of a worsening political climate.
''Right now, frustration is extremely high,'' says Brian Fitzgerald of Greenpeace New England and the New England Campaign to Stop the Euromissiles. ''It's extremely disheartening to put so much energy into an attempt and see it so easily subverted,'' he says.
In the past three months:
* The US Senate defeated the nuclear freeze resolution.
* The first Pershing II and cruise missiles were deployed in Western Europe.
* Congress approved funding for the MX missile.
* All superpower arms talks came to a standstill.
* The ''doomsday clock'' of the Bulletin of the Atomic Scientists, ''symbol of the threat of doomsday hovering over humanity,'' advanced one minute, and now stands at three minutes to midnight (nuclear war).
Given this bleak state of superpower relations, how do tiny nuclear groups or larger national associations maintain enough momentum to carry forward the ''nouveau'' peace movement, as one disarmament activist describes it? Are there new strategies?
''Most people understand it is a very slow process. It is not done overnight, '' Mr. Fitzgerald says. The day after the first cruise missiles began arriving in Britain last November, he remembers, ''everyone asked, 'What do we do next?' ''
The answer, Fitzgerald says, is: ''We educate, revise the literature, and make darned sure that the next president of the United States is going to do something. The first phrase everyone began to use was: 'They won't finish deployment until 1986. We haven't lost yet.' ''
Fitzgerald says, ''We have to constantly convince ourselves we have faith in humanity and the future. It just has to get better.''
Sometimes, however, it takes more than constant convincing to maintain morale and membership. There are those who simply cannot cope and ''burn out.'' But almost all groups - from the grass roots up - claim that as people drop out of the movement, there are as many, if not more, to take their place.
''Some burn out, others come in,'' says Bruce Cronin, disarmament coordinator of Mobilization for Survival, a national peace group with headquarters in New York. ''That's what a movement is all about. It ebbs and flows. There are times when it peaks more than others. Things change and we just try to keep the continuity going.''
Greenpeace's Fitzgerald calls it a ''growth cycle.''
''You can almost see new people coming in the front door and others going out the back door. Then there are always those who stick with it and have developed some sense of how to deal with the frustration and anger.''
Much of that anger has been directed toward Ronald Reagan - sometimes called the father of the US peace movement: It was the Reagan administration's massive arms buildup and initial playing down of arms negotiations - while voicing the possibility of controlling and winning a nuclear confrontation - that roused so many citizens to action.
''The Day After,'' last fall's television movie about a nuclear attack on Kansas City, brought the specter of nuclear war into millions of homes and, according to many peace groups, garnered thousands of new supporters.
The people coming in the front door of Women's Action for Nuclear Disarmament (WAND) since November, for example, have accounted for a ''25 percent steady growth on the national level,'' according to spokesman John Loretz in Arlington, Mass.
Nonetheless, he, too, speaks of demoralization. ''We hear frustration from all over the country. We have put together a diverse but cohesive movement - a very large and powerful movement - but it's knocking its head against the wall of the Congress.''
What that means, he explains, is that ''1984 will be very important. It will be a real test of the movement's strength.''
WAND's strategy for 1984, according to Mr. Loretz, is to target specific congressional races ''where nuclear weapons will be an issue, where it will be a close race, and where we are organized enough to make an impact in November.''
To Mr. Cronin, Mobilization's strategy is different. He suggests the ''important part is to continue to see the next step. You can't put all your efforts into one issue.''
He says each issue must be linked to a larger issue if the movement is to stay alive. If the freeze proposal passed in Congress, for example, many in the movement worry that supporters would pack up and go home.
''That's why we're not putting so much weight on the '84 elections,'' Cronin explains. ''The elections won't guarantee we will get a (nuclear weapons) freeze , even if we do get rid of Reagan. But we do need small victories,'' he continues. ''That's why one of the main parts of the disarmament campaign is to work on nuclear-free zones so people (in local groups) can see where they have an effect in their own community.''
Peggy Elertsen, an activist working on Freeze Voter '84 (the lobbying effort of the freeze campaign), is convinced the larger goal is still within reach. ''The issue is so personalized and so big that, even with the setbacks, this issue is not going to let go,'' she says.
''(Last) fall, many people were disheartened and were asking, 'What can I do?' or 'What can five or 20 people do?' But where we used to have meetings of 20, there are now 300 and greater.''
Mrs. Elertsen points to ''The Day After'' as a ''tremendous catalyst - flawed as it was - in rejuvenating the movement. It has drastically turned it around.'' She also says President Reagan has helped the movement by ''doing so very little in the name of peace.''
Donald Smith, a businessman who describes himself as ''an unabashed liberal but not an idealogue,'' has never attended a protest or a vigil. He volunteered to lead a peace group in his local church and is now a member of US-USSR Bridges for Peace, a Vermont-based project working for US-Soviet dialogue.
Since returning from a two-week trip to the USSR, Mr. Smith says he is more pessimistic - and is working harder because he feels ''a greater sense of urgency.''
''The basis for that pessimism is the degree of misfit between the two countries.'' Smith adds that, as a result, he ''is not under any illusions'' about the public's power to change government policies.
He suggests the answer is for the Soviets and the US to reopen diplomatic channels. ''Someone has to do a Sadat move,'' he says, referring to the late Egyptian President Anwar Sadat's historic trip to Jerusalem in 1977. ''Reagan might do it if he perceived the country wants it.''
Until the political climate improves, what keeps him going?
''I don't know. I suppose I lean on Christian humanity and Yankee common sense that we won't be dumb enough to wipe each other out.''