The new information from the 1980 Census affirms that it was the middle class, not the poor, who have been leaving Washington in droves. The poor were just being shifted around the city and forced to double up in overcrowded quarters, mainly east of the Anacostia River. Much of the rest of Washington gradually has been taking on a new, upper-class ambiance.

It's easy to see the evidence of this trend in a walk downtown.

The wave of neighborhood gentrification that has taken place in areas such as Capitol Hill, Logan Circle and Mount Pleasant has been accompanied by an equal wave of commercial development. Like the neighborhoods, downtown Washington is getting increasingly better for the more well-to-do.

Once moderate hotels are acquiring a veneer of luxury. Deluxe restaurants that spell m-o-n-e-y are proliferating, the new $98 million convention center will be a magnet for big bucks, and expensive stores are on the drawing board for the new downtown Washington. From the vantage point of renovated neighborhoods and midtown paper city, the city seems poised to prosper.

But this development won't be for the city's backbone--the stable, church-going middle class with long roots in Washington.

What plans are being made to attract and assure a place in the new, would-be Washington for this older black middle class and its younger offshoot, the young lawyers and other professionals--those who give this town its political, economic and social stability, those who make up the nontransient city that the tourists never see?

"D.C. has not done what it could to lure and hold its middle class," says longtime District watcher Dorn C. McGrath Jr., a professor of urban planning at George Washington University.

Make no mistake, there is still a middle class here. But if the trend in the census continues, Washington could become a city of only the very poor and the very rich. That would be unfortunate because a city with only the poor and the rich is a poor city indeed.

It's poor because the city needs upwardly mobile young professionals to provide the leadership structure, the entrepreneurial energy and the staying power to make the city work; poor because the city needs middle-class taxpayers.

Without a thriving, native middle class, Washington, in the extreme, might resemble a still half-colonized Caribbean island, with a solid upper-class elite on the one hand, and on the other, backwater neighborhoods of impoverished local have-nots serving those who have. That is a poor city.

In a rich-and-poor city, the poor would surely lose, as they so often do even now. The politicians don't assiduously court the poor, it's the middle class that votes. The public school system becomes a pauper's school system. There is no role model for those who grow up here and want to better themselves. A city of very poor and very rich is a city where the poor, when they move up, also move out--to the places where they can afford to live. The city does not rejuvenate itself.

The middle class is the real resource of a city, and it is a tragedy when the city loses it. Once lost, it is not easily recreated--witness the leadership vacuum in Anacostia, where only 7 percent of the residents are homeowners. There, it is an uphill fight to get the Metro Green Line subway system extended across the river at least to the Anacostia Station. There are few to lead the battle, and the politicians don't seem to be listening too well. Washington needs a middle class.

Our city is not alone in its shrinking middle class, but other cities facing the same dilemma--Baltimore, Boston, New Haven and even tiny Flint, Mich.--have managed to achieve a measure of success in luring back the middle class.

A rich-and-poor city lacks a hometown mentality, which is especially important in this capital city where so many of the rich are transient and so many of the poor are natives.

But in the end, the survival of the middle class ensures the city alternatives and a vision for the future.

And it will be that survival, not the current slide into dangerous polarization, that will make our city rich indeed.