Washington — Nuclear freeze proponents have declared the 1984 vote a victory for their cause. Trouble is, so have their arch-opponents, anti-nuclear freeze groups. A right-to-life leader says of the election, ''We won and we're glad.'' But a pro-abortion activist claims otherwise, saying the returns prove abortion has been defused as a political issue.
In Washington, just about every special-interest group is claiming its side won as a result of the Nov. 6 ballot. They are aided by what might be called natural optimism, and the fact that the congressional vote, in particular, can be interpreted numerous ways.
For groups that espouse causes associated with the Democratic Party, the trick is to treat the presidential race as a foregone conclusion, and talk about how the new Congress may be friendlier than they expected. Arms-control groups, for instance, say a number of nuclear freeze advocates in tough races managed to hold onto their seats. This, they say, represents a real victory for their cause.
''We made tremendous gains just by holding our leaders in office,'' says Mike Mawbry, spokesman for the Committee for a Sane Nuclear Policy. ''Ronald Reagan did not receive a mandate for his continued defense policies.''
On a number of controversial arms issues, say freeze advocates, the new Congress will lean their way. Although the GOP gained in the House, it did not gain enough to pass renewed aid for Nicaraguan rebels, arms control organizations claim. The MX missile survived a Senate test last year by one vote; with the Democrats picking up two Senate seats, the MX may be doomed.
''The MX is in more trouble than ever before. The MX can be and may well be defeated'' next spring, claims John Isaacs, spokesman for the political arm of the Council for a Livable World.
For conservative interest groups, of course, it's not very hard to portray last week's vote as a positive event. Pro-defense organizations say President Reagan's smashing reelection showed that US voters believe in peace through strength. In addition, they point out that freeze groups lost their only direct electoral test this year, a South Dakota referendum on support for ''a mutual and verifiable nuclear freeze.''
''Our survey research clearly shows that when the American people learn all of the facts, they overwhelmingly oppose the freeze,'' asserts American Security Council president John Fisher, who helped run a lobby campaign against the referendum.
The American Security Council's political-action committee, in addition, boasts that 90 percent of its endorsees won their congressional races.
Defense is far from the only issue where groups on both sides claim victory. Take abortion. Abortion rights supporters say their main goal - defusing the contentious issue - was reached. They cite a CBS News exit poll result that only one of every 10 Roman Catholic voters considered abortion before casting a vote.
No candidate lost because of a pro-choice stance, says Nanette Falkenberg of the National Abortion Rights Action League. ''The 'abortion scare' which has invaded national politics since 1974 is ending,'' she says.
Anti-abortion advocates, however, say they picked up 10 to 14 votes in the House, giving them some 260 lower-chamber supporters. In addition they have great hopes that Mr. Reagan will appoint anti-abortion Supreme Court justices. ''The pro-abortion groups would give their eyeteeth to be in our position,'' says John Willke, president of the National Right to Life Committee.
For Washington, D.C., interest organizations, a popular way of putting a positive spin on election results is to cite what percentage of the group's political endorsees won election. At the US Chamber of Commerce, political analyst Mick Staton says the business group won 182 out of the 211 races where it took sides, around 87 percent. ''Business will have things marginally better in Congress,'' Mr. Staton says.
Labor's victory percentage was somewhat lower, but still not bad. The AFL-CIO lost the presidential election in a big way, but it supported the winner in 63 percent of the lower races in which it backed candidates. In addition, labor was not sorry to wave goodbye to a number of conservative Southern House Democrats.
''We came out pretty good,'' says Ben Albert, an official at the AFL's Committee on Political Education.
Environmental groups were also not pleased about the presidential race, but still point to Congress as a positive sign. The Sierra Club and the League of Conservation Voters claim victory percentages of around 70 percent; in addition, they say Reagan has been forced to treat their issue more seriously. ''Reagan's not running around talking about trees causing pollution anymore,'' says Steve Pearlman of the League of Conservation Voters.