The most revealing thing about political scientist Jeffrey Berry's recent book ("The New Liberalism: The Rising Power of Citizen Groups") is that hardly anyone noticed it, even though its conclusion starkly contradicts conventional wisdom. After much research, Berry rejects the common view that liberalism died in the 1980s, suffocated by Ronald Reagan, wealthy business lobbies and conservative political groups. Judged by congressional legislation and press coverage, precisely the opposite is true. Liberal lobbies in Washington have flourished. They rival business lobbies in power and crush conservative groups, such as the now-defunct Moral Majority.

Since the 1960s, Berry says, liberalism's focus has changed from economic issues--redistributing income--to what he calls "postmaterial" lifestyle concerns: environmentalism, "rights" of all sorts, consumer "protection" and "clean" government. This liberalism mainly expresses itself through "citizen" lobbies, such as the Environmental Defense Fund, Ralph Nader's Public Citizen and the National Organization for Women. These are the lobbies that wield power in influencing Washington's agenda and shaping its news.

Based on my 30 years in Washington, this analysis instantly struck me as accurate. But with some exceptions (an excerpt in The Post's Outlook section, several National Public Radio interviews), the study has been ignored. Why? The answer is not that Berry is a right-wing zealot bent on exposing stealth liberalism. He's a Democrat ("I was raised as a Hubert Humphrey liberal") who has taught at Tufts University since 1974 and aims simply to plot interest-group power.

To do this, he investigated major congressional proposals in 1963, 1979 and 1991. What changed? Which issues got on the agenda? Whose views made it into the press? If Congress passed legislation, who won? By Berry's count, Congress considered--foreign policy, except for trade, was excluded--205 major issues in these years. (A proposal was rated important if it generated congressional hearings and some press coverage.) Here's what he found:

* Between 1963 and 1991, Congress's agenda moved to "postmaterial" issues. In 1963 about two-thirds of proposals were economic, typified by manpower training or farm price supports. By 1991 roughly 70 percent involved "postmaterial" issues, such as a wetlands conservation bill and the Family and Medical Leave Act.

* Liberal lobbies now receive highly favorable press coverage. In the printed press (Berry used the New York Times, the Wall Street Journal and the Congressional Quarterly Weekly Report), liberal groups represented almost half the quotations from lobbyists. Industry trade associations were about 30 percent, corporations one percent. Network TV news programs have a similar pattern.

* Liberal lobbies increasingly win. In 1963 business lobbies won three victories for every defeat by liberal lobbies. In 1991 business won three victories for every two defeats. Even this overstates business power, because often industry was simply repelling hostile legislation. Conservative groups, such as the Christian Coalition, had little effect on legislation.

Berry's study rebuts the notion that moneyed interests or conservative ideologues dominate Washington. The popular perception is different in part because the Republican capture of Congress in 1994 created a false impression of conservative triumph. To examine that idea, Berry looked at 12 environmental issues in the 104th Congress (1995-96). He judged that environmentalists won 10. Conservatives' power is also exaggerated because some of their ideas have prevailed. On economic policy, balanced budgets--in times of plenty--and low inflation now command wide support. So does "welfare reform."

But the central cause of misinformation--why Berry's study went unnoticed--is that people have a stake in it. Certainly, liberal lobbies do. They relish their image of impoverished groups fighting long odds against rich business lobbies. In fact, Berry finds that liberal lobbies are often well financed and highly professional. By contrast, conservative lobbies (but not business groups) are often poorly financed and poorly run. They have no interest in advertising their weakness.

The press, of course, should present a true picture--but doesn't. If it did, it would have to admit that it often aids liberal lobbies. This is less the result of a conscious effort to advance an agenda than of shared beliefs. Journalists see "the story" in the same way as liberal lobbyists. Business is regarded as greedy, self-interested and undemocratic. Conservative groups are "out of touch" or socially dangerous. By contrast, liberal lobbies are public-spirited "watchdogs."

The convergence of values is easily inferred from opinion surveys. Consider a 1995 poll of Washington reporters. Only 2 percent rated themselves "conservative," while 89 percent had voted for Clinton in 1992 (against 43 percent of the popular vote). Only 4 percent were Republicans (50 percent were Democrats, 37 percent "independents"). People with these values instinctively minimize the power of the "good guys" and make the "bad guys" look threatening. A lead story in the New York Times, for example, indicated that business dominated Congress's last session ("Congress Leaves Business Lobbies Almost All Smiles"). Actually, the story showed that business groups won a few modest victories and played defense on minimum wage and "patients' rights."

In a democracy, the vigor of liberal lobbies is healthy. They often succeed because they purport to speak for public opinion. Four-fifths of Americans, for example, see themselves as environmentalists, reports a Pew Research poll. What's unhealthy are the false stereotypes that distort who has influence. These discriminate against some views and popularize the idea that the political system--captured by "undemocratic forces"--is corrupt and unresponsive. In truth, politics often stalemates because public opinion stalemates. In that same Pew poll, almost half of Americans think that government regulation does "more harm than good." Our present stereotypes wrongly convert legitimate disagreement into a cynical conspiracy against the public.