The prevailing wisdom in Washington is that Americans, after the Cold War, fell into a sullen isolationism. We supposedly have no interest in engaging with other nations unless there's something in it for us. What must be done, we prefer to do alone, shunning cooperative actions with others. We resent foreign aid.

Washington policy-making elites swear by this picture of public opinion. Policies are set according to it: We withhold our dues from the United Nations, skimp on foreign assistance and wage war with a wary eye toward what the people think.

And now comes an intriguing new book to tell us that this view of public opinion is all wrong.

Two University of Maryland public policy experts, I. M. Destler and Steven Kull, set out to connect public opinion to the foreign policy process, suspecting a gap between the two. They found a chasm, as they tell us in "Misreading the Public: The Myth of a New Isolationism."

When Destler and Kull probed elite opinion in Washington -- interviewing members of Congress and congressional staffers, media people, executive branch officials and professionals in think tanks and other nongovernmental organizations -- they found that the policy-makers overwhelmingly hold the predictable set of beliefs.

The interviews yielded confident assertions that the public cares little about foreign policy. That opposition to foreign aid is widespread. That where there is involvement overseas, the public wants America to go it alone. And most important, that support for any foreign engagement is limited and will vanish at the first harm to an American.

This is what the public thinks, said official Washington.

Except that, apparently, it isn't.

Studying existing polls and conducting new ones and holding focus groups, the authors found that those assumptions about America's role in the world were way off the mark. They took the results back to the elites, who promptly rejected them: That's merely what folks say when you call them at dinner, they said. Go back at it with this kind of question, that kind of wording. Show them attack ads first. Force them to choose between candidates on the basis of foreign policy positions.

The two authors did what the skeptics suggested.

Their findings of public opinion held firm. There has been no decline in support for international engagement in the wake of the Cold War. The public embraces a vibrant role for America in the world, and particularly supports cooperative and multilateral international involvement, not the Great Power trips the elites said people favor when action is required.

Among the specifics the authors found: "Most Americans would like to see the United Nations become stronger, and want to contribute their fair share to peacekeeping missions." And, remarkably, "The public strongly supports foreign aid" and only "extreme overestimations of how much the United States spends" prompted calls for cutbacks.

In the course of their work, Destler and Kull frequently would encounter a firm conviction on the part of members of Congress and staffers that, for example, their constituents were adamantly opposed to payment of U.N. dues. The authors would then go to those very constituencies -- and find support for payment. Similarly, "When presented attack ads from two opposing political candidates, the majority approved the one who favored either foreign aid or the payment of U.N. dues."

How to explain the discrepancy between what people think and what the elites think they think? Destler and Kull said policy-makers presume too much from the views that come into their offices. For all the evidence that these views tend to be from voluble powerful interests not necessarily representative of the public, officials stressed that they consider them more trustworthy than polls. So they give more credence to the information they hear directly.

Similarly, there is little political corrective for acting on these misinformed views, because foreign policy questions rarely are decisive in determining whether a politician wins or loses an election.

In the end, Destler said in Washington the other day, the authors "just didn't find the skepticism, the negativism" that policy-makers assume. "When presented with factual information about the U.S. role in the world, what you find is overwhelming acceptance" by the public of the need for strong American engagement.

Kull added, "Policy-makers perceive that they're constrained by public attitudes. That's a myth."

It's not that policy-making should be mindlessly married to public opinion. But at least those who make policy ought to know what that opinion is. Members of Congress routinely defend neo-isolationist positions by saying they represent the public. As it turns out, they're governing according to the squeaky wheel.

"Misreading the Public" could be a powerful corrective.