The demise last week of the Equal Rights Amendment may have been cause for celebration by some of President Reagan's antifeminist supporters but there was no revelry at the White House.

Rather, presidential advisers are increasingly worried about another, quieter happening monitored by census data and public-opinion surveys that clearly show women not only voting in greater numbers but parting company dramatically with men--including Ronald Reagan--on key issues.

Indeed, Reagan's steady slide in the polls since his post-inaugural honeymoon period is the result to a significant extent of a slide in his job rating approval by women. A Washington Post/ABC News survey in May found that 52 percent of women disapproved of the way Reagan was performing as president while only 40 percent approved.

The views of men were just the opposite--52 percent approval, 42 percent disapproval.

Senior advisers at the White House are groping for a response to this trend.

Administration political strategists believe that economic issues and what one aide described as Reagan's "muscular statements on military affairs" are causing women to turn away from him.

"Women tend to be more pacifistic. They've always been that way," one aide said. "It has never been thought that the women's issues per se have been the guiding force" of the opposition.

Senior aides insist, as Reagan himself did at a press conference Wednesday night, that the president is committed to equal rights for women even though he opposed the ERA. But the aides also acknowledge that the major concerns of women have not been at the top of the White House agenda--but are moving up quickly as the poll results come in.

That still leaves the question of what to do. One aide compared the situation with standing on railroad tracks, watching a locomotive speed toward you.

In recent weeks, presidential advisers have attempted, in the words of one, to "breathe new life" into administration initiatives to fulfill Reagan's campaign pledge to remove sexist and discriminatory provisions from state and federal laws.

Although Reagan supported the Equal Rights Amendment when he was governor of California, he disavowed that endorsement when he ran for the GOP presidential nomination in 1976. In the 1980 campaign, he said he believed a constitutional amendment would only increase the activism of the courts but revision of the laws would better accomplish the equality women are seeking.

He said he was for the "e," the "r" but not the "a."

Wednesday night, Reagan referred to such efforts as his "50 States Project," aimed at working with governors and state legislators to amend discriminatory state laws, and its federal counterpart, the Task Force on Legal Equity for Women.

What Reagan did not mention was that the part-time position of coordinator for the "50 States Project" was vacant for three months until late June.

The Task Force on Legal Equity for Women has not been much more active. It found that its assigned task of identifying discriminatory federal laws had been substantially accomplished in the Ford and Carter administrations.

As a result, it has shifted its focus to federal regulations, concentrating on cosmetic changes in language--altering federal regulations referring to "seaman" to say "sailor," "chairman" to "chairperson", for instance.

Some women at the White House regard with sharp irritation the fact that the discussion of how to solve Reagan's problem is the province of an exclusive coterie of white males.

Many observers believe that much of the problem is the fact that Reagan and his top advisers are of a generation and political orientation that is not sensitive to women's issues. Others believe that Nancy Reagan hinders such sensitivity.

One well-positioned woman in the White House, who has worked in other GOP presidential campaigns in which women had important roles, said that when she joined the Reagan camp she immediately felt a different attitude toward women. This attitude, she said, carried over into the White House.

It is neither rudeness nor insult, she said, but more a myopic tendency to look on women as secretaries doing the typing, filing and running out for coffee.

She does not consider herself a "women's libber," nor was she much saddened by the death of ERA. But she bristles when describing what she considers an amiable but condescending and pervasive attitude toward women at the Reagan White House.

She complains that women are frequently overlooked when it comes to promotions even though many secretaries and executive assistants are given responsibilities beyond their routine chores.

Still, the two women generally regarded as having the most influence in the Reagan White House have moved upward along that route.

Helene von Damm, Reagan's secretary since his Sacramento days, asked for and got major fund-raising responsibilities in the 1980 campaign. In the beginning at the White House, she returned to her secretarial position but was later sent to the White House personnel office to help with problems there. A formal announcement naming her head of the personnel office, which has been the de facto situation for several months, is expected soon.

Margaret Tutweiler, a younger woman who is chief of staff James A. Baker III's executive assistant, is widely viewed as similarly rising in influence and responsibility. Senior male aides describe how she has begun to push issues affecting women in meetings. Respect is growing for what they describe as her keen judgment.

There are other well-regarded women working as secretaries or executive assistants who still balance typing, filing and answering phone calls as their other responsibilities, but not positions, rise. Some, not all, resent it.

Elizabeth Dole, the White House assistant for public liaison, is regarded as handling her job well, but she is thought not to have penetrated the "loop" of power in the White House. Neither she nor other women who are full-fledged aides in the White House have achieved the influence and access to the power as Tutweiler and Von Damm.

Von Damm says she is organizing a task force to identify women who can fill the jobs she is sure will open up through normal turnover after the mid-term elections.

But she insists that "the best-kept secret in town" is Reagan's record of appointing women, which she claims rivals that of the Carter administration. Overall, Reagan's more than 400 appointments of women to patronage-level positions about equal Carter's in his first 17 months in office.

But Reagan's appointments include more part-time boards and commissions. Carter had three women running Cabinet agencies. Reagan has none, although U.N. Ambassador Jeane J. Kirkpatrick has Cabinet rank.

Reagan was the first president to appoint a woman, Sandra Day O'Connor, to the Supreme Court, but has not appointed any to the federal appellate courts and, in filling 50 vacancies in the trial courts, has appointed only three women. All 11 women on federal appeals courts and 30 of the 35 women judges in federal trial courts were appointed by Carter, according to the National Women's Political Caucus.

Pollster Lou Harris said last week he believed that "one of the major developments" of the 1980s would be the emergence of women as a "powerful new force in American politics," which he said could be as significant in politics as the rise of labor in the 1930s.

Harris finds that men and women are beginning to differ on a range of key issues. In one recent poll, a majority of women, but a minority of men, indicated that they were concerned that the world will "be plunged into a nuclear war."

There was a similar division about the recession, and Harris found that women worry far more than men that next year "more people will be going hungry," "more factories will be shutting down" and "more people will be losing houses and farms because they can't meet the mortgage payments."

Harris said that as the number of women who work has grown from about one in three two decades ago to slightly more than one in two today, the indications are that they have more pride in their ability to make a contribution in politics.

He said that women are now inclined to think that they are discriminated against in wages and promotions but a majority of men polled disagreed.

"Women are now a new force in society," Harris concluded. "And as they come into their own in the world of employment, they are becoming more political than ever before. Their political weight will be felt increasingly throughout the 1980s, and the chances are good that the struggle over the passage of the ERA will be recorded in history as the turning point."