WAYNE HAYS, who liked to call them "Common Curse," always enjoyed telling John W. Gardner still his hand of do-gooders what they really were.

You're just a bunch of lobbyists," the cantankerous Ohioan would snarl at the people from Common Cuase. "You're just like the oil lobby or the farm lobby or any of the rest of them."

In the harsh, deprecatory tone of voice that Hays made famous during his years in Congress, it sounded like a severe condemnation. But to Gardner, who dreamed up the "public affairs movement" called Common Cause seven years ago and built it into a formidable force on Capitol Hill, Hays' attacks came as something of a compliment.

"If you look at things from the perspective of 1970, I guides we ought to be flattered when that kind of thing is said, "Gardner observed in an interview the other day.

"Back then there were people saying we would never amount to anything. I mean, they hooted. Some congressmen were outraged that we would even try this. But now, if they know us as well as they know the established 'issue lobbies,' I suppose that means the organization has made a mark."

The organization clearly has. Indeed, as Common Cause embarks this month on its new, post-Gardner phase - the founder has just resigned his post as the organization's chairman - the argument could easily be made that it is the most influential lobby in Washington.

This is so because the changes Common Cause has pushed for are more fundamental than those sought by the standard "issue lobbies."

Under Gaardner's direction, the organization has concentrated on the processes, rather than the products, of government. There is disagreement whether all the "process" changes effected by Common Cause are for the better; the campaign spending limits for which it fought, for example, were slapped down by the Supreme Court as contrary to the First Amendment. But no one can disagree that Gardner's lobby has been remarkably successful in doing what it set out to do.

Common Cause has had a significant impact on laws regulating campaign contributions. It played a central role in the passage and the legal defense of public financing for presidential elections. It has been promoting public funding of congressional campaigns for some time and is now deeply involved in the effort to pass a campaign fund bill this year.

Within Congress, Common Cause has been a persistent and generally successful gadfly on ethics, conflict-of-interest, financial disclosure and lobbying. Although it has not eradicated the seniority system - one of Gardner's original goals - it has knocked a considerable dent in the tradition. In the case of Rep. Robert Sikes (D-Fla.), Common Cause last year forced the House Ethics Committee, for the first time in its hsitory, to do something about a member's ethics.

In Washington and in about two dozen state capitals, Common Cause has been a leader in efforts to open up the work of government so the people can look inside.

The organization has provided invaluable assistance to other lobbyists and observers of government. After each congressional election. Common Cause workers have undertaken the tedious task of cataloguing and categorizing who contributed what to whom.The resulting volumes are used regularly by reporters, lobbyists and future candidates.

Common Cause has also served as a model for other "citizens' lobbies," ranging from the Ralph Nader organization Public Citizen to the new Washington-based group New Directions, which will take a Common Cause-like approach to international issues such as nuclear proliferation. A Certain Smugness

THE LONG string of successes, and the outpouring of praise it has generated from the media, have led to an inevitable smugness at Common Cause. The organization's publications and press releases generally portray Common Cause as God's gift to the American people - and John Gardner as close to God Himself.

To hear Common Cause tell it, Common Cause's interests are invariably "the public interest." A Common Cause proposal is never just a change; it is a "reform." Common Cause itself is not just another lobby; it is a "people's lobby" or, in Gardner's preferred phrase, a "citizens' lobby."

All that can grate, even on the organization's allies. Gardner, a pensive but amiable man of 64, recognizes the problem.

"I think it's a little presumptuous to call ourselves a 'public interest lobby,' or to say that we're 'the people's lobby,'" Gardner said. "I can see why that would raise eyebrows, and personally I practically never use these terms."

The founder is peeved, nonetheless, at reporters who describe Common Cause as a "self-styled people's lobby."

Although that phrase is accurate, it is "pejorative," Gardner says. Indeed, Gardner once offered The New York Times a list of six possible appositives - ranging from "citizens' lobby" to "public affairs movement" - so the paper could accurately describe just what Common Cause is.

Common Cause is 253,000 people throughout the country who support the organization with an annual dues payment ($15, although many send in more) and occasional volunteer work on local or national Common Cause projects. These quarter million members represent the "people" of the "peopel's lobby," but they do not reflect a very wide sociological swath of the American people as a whole. As The Post's David Broder has observed, "Common Cause is anything but common folks." It is mainly an elite group of upper-income, highly educated, liberal suburbanites. Although Gardner has managed to attract many people who say they have never joined anything before, there is substantial overlap in membership with such groups as the American Civil Liberties Union, the Leauge of Women Voters and the environment-minded Sierra Club.

To determine what its common causes will be, Common Cause's Washington staff meets quarterly with a 60-member board elected by the membership. The agenda for each board meeting, in turn, is supposed to be based on a referendum in which the members across the country set priorities for the Washington office.

In practice, however, the membership's priority-setting is done in sweeping generalities; the specifics of which bills to work on, and what positions to take, are determined by lobbyists in the Washington office. Last year, for example, the membership voted priority to "overhaul and revitalization of government." From that broad mandate, the Washington staff began working for scores of specific bills, arguing each time that 250,000 Common Cause members were behind the legislation. Fooling the Experts

ALL THAT was predictable in the summer of 1970 when Gardner began placing newspaper ads - "Everybody's Organized but the People" - and mailing hundreds of thousands of flyers seeking members for a "new, independent non-partisan organization for those Americans who want to help in the rebuilding of this nation." Columinsts and congressmen - even those who professed deep respect for Gardner personally - saw in it just one more good-government group that could do little more than send liberal-leaning newsletters to people who already had liberal leanings.

"A by-product of cosmetic liberalism in Washington," scoffed columnist John P. Roche. "A sonorous organization to benignly flaccid liberal goodwill," agreed Nicholas von Hoffman.

But Common Cause fooled the experts. It has, true enough, produced its share of sonorous speeches and liberal newsletters, but it also has produced more concrete legislative achievements than any of its fellow "public interest" organizations.

Why? The secret of Common Cause's uncommon success is partly an accident of timing. Gardner's group started working for such goals as open government and political campaign controls in an era when the Pentagon Papers and Watergate were making it painfully clear how badly such changes were needed.

But Gardner and his corps of lobbyists - led by David Cohen, now Common Cause president, and Fred Wertheimer, now second in command - deserve considerable credit for bringing a new professionalism to "public interest" lobby work.

They carefully chose the issues on which they would concentrate, so as not to dissipate their strength on scores of good, but hopeless, ideas. They worked to develop allies in Congress - frequently targeting particular members for grass-roots lobbying campaigns from the organization's members back in the districts. They did their homework, and established for Common Cause an estimable reputation as a knowlegeable, and thus credible, lobby.

Gardner, a one-time psychology professor turned foundation president who learned how to deal with Congress while serving as HEW Secretary in Lyndon Johnson's cabinet, says Common Cause's strongest weapon is its consistency.

"We had a definite point of view, and we held to it very, very consistently," Gardner said.

"When we went after the [House] committee chairmen we thought were tyrannical, for example, we included Wright Patman, on the Banking Committee even though most of the public interest people around were great defenders of his. But Patman had abused his position, and we would not let up.

"Members of Congress take note of that kind of consistency."

One man's "consistency," of course, is another's "obstinacy," and Gardner's stubborn determination to achieve his goals sometimes disturbs other members of the "public interest" community here.

"All of us recognize that Common Cause has been tremendously helpful," says Alan Morrison, of Nader's Public Citizen. "But sometimes we wish they would look at the arguments on the other side."

"They have pushed for financial disclosure by government officials," says Morrison, who opposed Common Cause's version of a bill to control lobbying by putting all contacts on the public record. "Which is fine, but there are some problems, some real privacy problems, that shouldn't be ignored. Common Cause is emphasizing disclosure for disclosure's sake - without any thought to the implications for individuals."

If anyone at Common Cause is concerned about such things, it is not evident to a visitor at the organization's national headquarters. The offices, sprawling over a full floor of an office building at 20th and M Streets NW, are suffused with an aura of cheery busyness not unlike that of a winning political campaign. The 92 salaried employees and an omnipresent corps of gung-ho volunteers scurry here and there to send out the latest newsletter or compile data from the latest survey or prepare position papers on the latest congressional cause.

What the office lacks is the scruffy, second-hand look of the nooks and crannies around Dupont Circle where most of Washington's "public interest" community works. With an annual income of $6 million in dues and contributions, Common Cause has always been the rich kid on the public interest block, and that garners some resentment from allies in the Nader groups and other such organizations.

Common Cause people are well paid and well cared for. Lobbyists commonly earn more than $25,000 annually, with some top salaries around the $40,000 level. Cohen, the president, inhabits a spacious office, complete with private bath, that would do quite nicely for the fattest cats in the oil lobby. When he travels to the Capitol on a lobbying mission, Common Cause's chauffeur drives him in Common Cause's car.

Things are a little more earthy in the state offices, where the organization has a total of 52 paid workers. Typical of the state operations is the Virginia headquarters in Richmond - a hole-in-the-wall down the street from the statehouse manned by a single lobbyist who earns $1,500 for each legislative session. Changing the Goals

GARDNER says that more emphasis will be placed on Common Cause's state lobbying efforts in the future, with the regional operations basing their work on the issues and tactics that have been so successful in Congress over the past seven years.

"We haven't gotten everything we hoped for in Congress," Gardner says, "but overall we've achieved a great deal in reforming the way the legislative branch does its work."

Accordingly, in its Washington operations the lobby intends to shift much of its attention toward the executive branch of government, in an effort to make the working agencies "open and accountable to the American people," in Garndner's phrase.

"We're not turning our back on Congress by any means," Gardner says. "For one thing, we're going to have to work hard to keep nailed down the stuff we've already gotten.

"But there's going to be a new focus. The executive branch is a whole new line that's largely untouched. We're going to look at government contracting, leasing procedures, the lobbying that goes on in the agencies, conflict-of-interest - those agencies will be fertile ground."

John Gardner will not be among those tilling that fettile soil, however. He has moved up to the emeritus position of "Founding Chairman," and he says his role in the organization from now on will be to look out for signs of "decay."

"I used to think that, if you understand the process of maturity and decay, you could design an organization that could avoid it," he says.

"Now I don't know. I'm afraid the things that bring about decay are so deeply rooted in the human psych that you can't avoid it."

In his book "Self-Renewal," Gardner concludes that "new challenges" are essential if individuals and organizations are to remain vibrant.

Will there be sufficiently challenging tasks in Commom Cause's future?

"That's question I've been thinking about," Gardner says. "It's pretty hard to think of a thing that's going to be as revolutionary as passage of the campaign financing legislation.

"But then you look at what we're going to be working on in the future.The day we can get a middle-level bureaucrat in some federal agency to realize that he is accountable to the people for what he does - that is going to be a very challenging day to get to."