The "good vibes" that pervaded the National Women's Conference here sent the 2,000 delegates and alternates back home today believing that their four-day meeting marked another important step in their struggle for greater power and policy change in this country.

But as Margaret Costanza, assistant to the president and a speaker at today's closing session, said in an interview, "when the euphoria is past, we will realize that we still have the hard work to do."

That is as true of the immediate battle over ratification of the Equal Rights Amendment as it is of the long-term effort to place more women in political office and build support for the ambitious set of policies endorsed by the convention.

Most of those inside the hall agreed with Jane McMichael of the National Women's Political Caucus that despite their fears that it would be marred either by rancorous divisions or monumental confusion, "it turned out to be a very positive thing."

But, like the national party conventions, the women's conference is likely to be measured less by the mood it created inside the hall than by the impression it left with spectators. And there the effect is not nearly as clear.

The ERA battle is the prime test of strength. Stymied three states short of the 38 needed for ratification, the amendment's backers have only 16 months to push it through, unless Congress extends the ratification deadline.

The one-sided endorsement of ERA late Saturday night triggered the most emotional outburst of the conference. As women chanted "Three More States, Three More States," it was easy to believe that their fervor alone would sway the relative handful of state legislators blocking its passage.

But the one-sidedness of the ERA vote also reflected a political imbalance among the delegates chosen by their state conventions that skewed the tone of the whole convention. Because there was no significant conservative bloc to be dealt with, the main effort of the "pro-plan" caucus representing the majority of the delegates was to avoid fights with the organized activists speaking for such groups as welfare recipients, minorities, the handicapped and lesbians.

The proposal opposing discrimination against lesbians in anything from employment to child custody was regarded as a civil rights question by most of the delegates. But it troubled many in its political implications. Betty Friedan, one of the leading spirits of women's liberation, said in an emotional speech that she had always opposed tying the movement to the lesbian cause, but now felt the rights of female homosexuals had to be protected. But there was significant support, too, for the Georgia delegate who said the endorsement of lesbian rights "is an extra burden" on those struggling to gain ratification of ERA in states like hers.

Rosemary Thomson, an anti-ERA leader in Illinois, and Patricia Hutar, an active supporter of ERA from the same state, both said they doubted the weekend's actions here would have significant effect on the battle in the Illinois legislature, a principal target of the final drive for ratification.

Thomson said the conference's endorsement would be discounted by the public's and politicans' perception that it was controlled by "radical feminists." Emphasizing the difference between issue politics and elective politics, Hutar said passing ERA resolutions would do nothing in Illinois "unless we can elect some of the 30 pro-ERA women who have filed for the legislature next year."

Thomson and Hutar are interesting in another respect, because they are both active Republicans who shared an identical early allegiance to Barry Goldwater and now find themselves diametrically opposed on women's issues.

Because the women's movement in its early years was symbolized by liberal Democrats like Gloria Steinem, the impression has been that Republicans have little part in it. But that impression is no longer accurate - as evidenced by the involvement here of former First Lady Betty Ford, current Republican National Committee Co-Chairman Mary Krisp, former National Chairman Mary Louise Smith, and former Co-Chairman Elly Peterson, along with more than 250 Republican grass-roots delegates and alternates.

Krisps involvement in the women's movement has become a matter of increasing controversy within party leadership circles, and conservatives may try to force her outser next year. It appears likely that women's rights may prove as divisive an issue inside the GOP in the 1970s as civil rights was in the 1960s.

As for the Democrats, they have a different problem. The women's caucus has played an increasingly assertive and influential role inside the Democratic Party in the last conventions, osmetimes jarring older parts of the Democratic coalition. One female labor official here said she saw growing evidence of a labor-women's coalition, citing the warm reception United Auto Workers leaders recently gave to a guest appearance by Eleanor Smeal, head of the National Organization of Women. But when asked how she thought George Meany would react to this convention's endorsement of lesbian rights, she just winced.

Ultimately, of course, politics in this country is concerned with elections, and there the women's movement is still years away from reaching its potential. While their numbers have increased slightly, women are still a tiny minority in Congress, the state Ann Saunier, the Columbus, Ohio, personnel manager who is one of the capitols, and the major city halls.

The irony of the situation was pointed up today in a comment by principal heroines of this conference. Saunier, a NOW member who had never presided at a gathering of more than a dozen people before last-April, handled the gavel during the emotional debate on abortion and lesbianism with a skill that even Sam Rayburn would have admired.

When asked what she thought would be the lasting importance of the meeting, she resplied that "the main thing is that our program goes to President Carter, and he is required to respond to it by making his own recommendations to Congress. We can find out now how committeed he really is to women's issues."

Someone said, "So once again, you are waiting to hear from a man." Saunier replied, "that's the reality - for now."