"I was thrilled," Democratic Lt. Gov. Madeleine Kunin told about 130 listeners at a luncheon of the Rutland Women's Network the other day, "that I made my maiden speech in the legislature on behalf of the Equal Rights Amendment. But I have evolved. And I understand that it is going to take more than a line in the Constitution to secure equal rights.

"So I was equally thrilled today, campaigning in Vergennes (a town of 2,273 people) to meet a woman pharmacist -- there aren't that many in Vermont -- and a woman mortgage loan officer at the bank."

What Kunin was talking about -- and what she symbolizes herself in her quest to defeat three-term governor Richard A. Snelling, a Republican -- is the most important development in the push for equality of American women.

The word that activist women use for the phenomenon is "mainstreaming." It has dual meanings. At the individual level, it means deliberately putting yourself into the center of the contest for power, instead of being content with titles that sound important but are empty. That is what Kunin herself is doing in what she calls her "underdog" effort to dethrone Snelling.

She has been lieutenant governor for two terms, filling a pleasant but empty office that has been a convenient waiting-room for the ambitious.

When she announced for governor, a year ago, the widespread assumption was that Snelling would be stepping down. He announced his retirement plans but, four months later, changed his mind. Kunin did not back off, as everyone had expected. She did not "wait her turn."

But she is also an example of the fact that for women entering the mainstream of politics, the challenges never stop; they just get tougher with each step. Kunin is conducting a thoroughly competent, well-financed campaign, with plausible position papers on the issues facing the state and assiduous courting of its farm and city constituencies.

What she has not yet done is to give the voters any clear statement of why the incumbent should be involuntarily retired. And since Snelling is an able, articulate executive, with a degree of renown as the recent chairman of the National Governors Association, he is not going to oblige her by defeating himself.

The second meaning of the word mainstreaming may be even more important. It describes the issues. The movement is going beyond merrily defined "women's issues," including ERA, and into the "mainstream" of politics, which now, as always, means the pocketbook-economic issues.

The shift to economic issues has come not just because the demise of ERA coincided with the deepest recession in 40 years and not just because of the increasing documentation of that ugly phenomenon called "the feminization of poverty."

It has come because women leaders have been hearing from their constituents, who have economic injustice on their minds. Whether it is a successful Republican businesswoman like Mary M. Riche of Des Moines, still angry over the refusal of credit by her bank after her divorce, or Boston Service Employes Union president Dorine Levasseur, telling a Women's Equality Day rally last week that "dog pound attendants -- mostly men -- are paid more than children's day-care center employees, who are mostly women," the economic issues are at the forefront.

As women move to the "mainstream issues," their impact is likely to grow. Kunin suggested hope that the success women have had in creating rape crisis centers and safe houses for battered spouses could well become a model for "a change in the pattern of callous neglect of other victims of crime by our criminal justice system . . . the elderly person who has his wallet stolen, the shop owner who is the victim of a burglary, the youngster whose proudest possession, a car, is stolen. They need compassion, too."

What we are witnessing here is a familiar and heartening phenomenon. As President Carter liked to remind the nation, the black civil rights movement liberated whites from the burden of prejudice as it liberated blacks from the burden of discrimination. Women's quest for justice will, in time, bring all of us -- men as well as women -- steps closer to that elusive eternal goal.