For many years in Washington, some political observers have held the notion that there is a "master plan," orchestrated by rich whites, to systematically rid the city of blacks and the poor by manipulating city elections and raising the prices of housing dramatically.

If the master plan did what it was supposed to do, some say, Washington would become a southern version of the Upper East Side of Manhattan: a haven for an upper-class, mostly white population.

The notion of a master plan would seem to be supported by the latest census figures, which show that predominantly black Washington lost 27 percent of its middle class in the past 10 years. But some city politicians and demographers say the census figures show something different: that the middle class is becoming more important to the city and in city politics.

According to the U.S. Census Bureau, the middle class includes families earning between $10,000 and $50,000 annually. About 63 percent of the families in the city fall in that category.

While the middle class decreased by 27 percent,the number of upper-income households (earning more than $50,000 a year) increased 4.1 percent and the poor (those earning below $10,000) increased by 6 percent.

But despite the loss of middle-class families shown in the Census Bureau reports, many politicians in the District and political strategists seem indifferent to the changes in the audience that they will have to play to on election day.

"What you have to realize is that poor people never have voted very much," said Dianna Brochendorff,ager of Betty Ann Kane's mayoral campaign. "But neither do the rich. The poor are disenchanted and the rich aren't really that affected. It's still the middle class who are going to vote and organize. The change you will see is that they (the middle class) are going to become much more up-front about their needs if they feel they are being squeezed out.As the middle class shrinks in the city you are going to see politicians paying more attention to them," Brochendorff said.

Brochendorff and others involved in city politics point out that the biggest turnout of voters in recent elections is still to be found in Wards 3 and 4, by comparison two of the city's richest areas with the highest concentration of middle- and upper-income residents. In last year's Ward 3 School Board race, for example, in which Wanda Washburn defeated Mary Ann Keefe, more than 15,500 voters went to the polls. In the same year, a seven-person race in Ward 8, a comparatively poor area of the city, drew fewer than 3,000 people to the polls.

Meanwhile, the recent census figures also suggest another trend: Wards 1, 2 and 6, the central wards in the downtown area, seem to be changing to areas that are more middle class and not increasingly poor or rich. While those areas all have lost population in the last 10 years, the people they lost seem to have been the poor.

Those wards are the areas of the city where young blacks and whites increasingly--either single or, if married, childless--have been the most active in buying and renovating damaged old houses. They have displaced the large, relatively poor families who lived there through the riots and the crime. Many of those poor families have followed middle-income families to the suburbs.

"The people drawn into the District in recent years," said Eunice Greer, a demographer, "tend to be singles or empty nesters--childless couples. . . . In addition, you had a significant decrease in the size of the average household in the city (down a third of a person, according the Census Bureau). What this means in terms of money is that even a moderate income, like $15,000 or $20,000 for one person, means that person is essentially well-off. It also means that if you have two people working and making $100,000, they basically have middle-class conce because they are in the city and concerned with city services, crime . . . ."

In the changing city, then, are the major political issues any different?

According to some politicians and demographers, the issues will not change that much. Crime may be more important to single, well-to-do people than to people in families; jobs and economic development will not get jobs for the middle class but will keep their taxes down by providing a larger tax base; and proposed housing programs that include subsidies to help young middle-class singles afford down payments as they tire of paying rents remain important.

"Even the schools remain a big issue," said Stephen Diner, chairman of the urban affairs department at the University of the District of Columbia. "The assumption that everyone makes after looking at the changes in the city's demography is that education, a middle-class family concern, will be in political trouble. But we've never had more effective lobbying for schools than in the last two or three years. I think middle-class people staying in the city realize they have to get involved and in the absence of any political machine here, the more organized the middle class are, the stronger they are."