A river of people, ordinary city people, flows steadily past the White House -- all day, every day, rain or shine or Ronald Reagan.

Well-dressed drivers in sleek Mercedes, unceremoniously being honked out of the way by vintage Motown junkers. Office workers threading their way down the sidewalk through clumps of camera-laden tourists. Small children with large dogs. Sour-faced but cheerfully clad runners taking joyless laps. Teen-agers striding in time to their portable stereos, the big loud boogie boxes that some whites smirkingly call "minority briefcases."

These Washingtonians peer through the imposing black wrought-iron gates as they pass. Did a curtain just move at an upstairs window? Is somebody, anybody, looking out? At us?

The advent of a presidency is always a watershed occurrence in this town, with implications for the style and substance of Washington life. But because of the times and the man, the arrival of Ronald Wilson Reagan, 40th President of the United States and newest lodger at the big mansion in the middle of town, has been met in this predominantly black Democratic stronghold with unusually intense anticipation -- mostly pessimism, but with the lightest dusting of hope.

Not everyone allows that it makes a dime's difference who lives at 1600 Pennsylvania Ave, to the 635,185 people in the District of Columbia's neighborhoods. Particularly nonchalant are some Democrats who sould just as soon pretend the Reagan administration is nothing more than a temporary aberration or a bad dream. Not to mention the Republican-controlled Senate. a

"i don't think there's any great difference except to that small percentage of people who are fighting for invitations to all the parties and over who gets to be the social queen," said lawyer Joseph L. Rauh, a life-long Democrat who came to Washington two years after Franklin D. Roosevelt's first inauguration and has stayed to watch subsequent presidents come and go.

"there are only maybe 400 or 500 people that the change has any real impact on," Rauh grumbled. "Me, I'll play tennis. Anyhow, my view is that it'll take Reagan so short a time to blow it that the Democrats will be back soon anyway."

Others disagree, including people from parts of town that seem as far removed from the pristine White House grounds as Venus from Mars.

"I think this inauguration is provoking a greater range of feeling than any other I have known," said the Rev. Ernest R. Gibson, who goes back to the Eisenhower years. Gibson is pastor of First Rising Mount Zion Baptist Church in the heart of the inner-city Shaw neighborhood, one of the District of Columbia's major pockets of desperate poverty.

It is a place full of disemboweled rusting cars and abandoned houses, junkies and pimps, beer cans and broken bottles -- but also tidy brownstones newly rehabilitated by affluent newcomers, "urban pioneers" moving to the central city because of the convenience it affords and the comparative bargains to be found in real estate. Relations between the old Shaw residents and the newcomers often are strained.

Worshipers in Gibson's all-black congregation have made Reagan's arrival a major topic of conversation and concern. "You have on one end of the spectrum a hope, born of despair, that the new administration can do something -- the feeling that there's nowhere to go but up, that maybe he can do something about inflation and joblessness," Gibson said. "But on the other end, there is fear."

The specific fear is that Reagan, coming into office at a time when the national mood has apparently shifted to the right, may conclude that he has a mandate to cut back social programs on which many low-income Washingtonians depend for survival. Local officials have long maintained that the District is uniquely dependent on these federal monies since it is entirely an urban entity, having no rich suburbs or productive farmland to tax for support of local programs.

But there is also a more generalized unease, say Gibson and others, among blacks who see a deeper change in the sociological climate heralded, for example, by the widespread publicity recently given a resurgence of groups such as the Ku Klux Klan. The feeling in this post-civil rights, post-Bakke, post-everything era is that no one should expect any new favors from on high. Or even much sympathy.

Physical miles and metaphysical lightyears distant from the streets of Shaw are the tree-lined avenues of far Northwest. Here, houses are large and sidewalks queaky clean. Nights are quiet, free from the wailing sirens that scream of violence and death and affluent area of the city west of Rock Creek Park is represented on the City Council by veteran Democrat Polly Shackleton.

No fan of Reagan, Shackleton has a diffenent set of worries that stem from her role as part of the District's limited-home-rule government. Jimmy Carter was an outsider when he came to Washington in 1977, but he chose for his Cabinet a number of familiar local fixtures, such as Patricia Harris and Joseph Califano.

Not only is Reagan an outsider, but his people are outsiders as well. No one in the city government really knows them.

"we have to build up a whole new set of relationships." Shackleton said. "We'll be starting at ground zero. We've got a lot of new people to meet."

Knowing the people in the White House is crucial to the city's elected officials because of the network of relationships and dependencies between the federal and District governments.

Despite home rule, the White House and Congress must approve the city's budget each year before a penny can be spent, even out of the city's own revenues. The District also depends on Capitol Hill for an annual federal payment in lieu of taxes on federal lands, which take in about half the city.

The federal government depends on the District for services such as the word of the D. C. police department in handling countless demonstrations and all of the other hoopla the city must play host to as seat of the country's political power. When farmers rode into town on their tractors, they left behind a major mess that someone had to clean up.

Presidents have been key to the city's quest for self-government. John Kennedy was the first to designate a full-time staff member to look after District concerns, and Lyndon Johnsonbrought the first seeds of home rule by authorizing an appointed mayor and council.

Richard Nixon performed a small-scale version of his celebrated opening of China one year and played Santa Claus in another. Shortly after taking office in 1969, Nixon toured Shaw and , on Christmas Eve in 1973, he signed legislation allowing District residents to establish their first elected government. Carter supported full congressional voting rights for the District -- a goal still unattained -- and generally took a hands-off attitude toward the city's finances.

Not all presidential impact has been so benign. Woodrow Wilson is generally credited with reestablishing racial segregation in what was then a relatively wide-open city. Nixon branded the District with its still unshaken reputation as crime capital of the nation and beefed up the city's police force to a level many local official now believe is wasteful.

"The president specifically sets the tone for how the nation's capital is going to be viewed in relationship to the national government," said Walter Fauntroy, the District's non-voting delegate to Congress. "It just makes an enormous difference."

During the presidential campaign, Reagan either opposed or took no stand on most District home-rule issues.He stood outside the Alamo in San Antonio one day last summer and suggested that, if the District wanted representation in Congress, it should again become part of Maryland. Local officials hope now that he will reevaluate his positions or at least leave things where they are.

"i don't think he'll really turn back the clock" is an opinion voiced often but somewhat nervously, at the DistrictBuilding, Washington's city hall, these days.

The underlying question is whether Reagan will take a liking to his new neighborhood. It is an immensely varied city, most of it looking and feeling nothing like the neoclassical precision of the Mall and the Federal Triangle, or the slick glamor of the new downtown where lawyers and lobbyists work, eat quiche for lunch and shop for baubles in expensive boutiques.

There is the H Street NE corridor, still in shell shock from the 1968 riots that followed the murder of Rev. Martin Luther King Jr. It is a long, depressing row of battered, shuttered storefronts interspersed with surviving businesses, liquor stores and barber shops bunkered against the streets with heavy metal gates.

There is Anacostia, equally distressed, the separate city across the river that many short-term Washingtonians and a lot of long-term ones never see. There is the sleepy Southern town spread throughout the northeast quadrant of the city, a collection of solid, mostly black, churchgoing neighborhoods of detached homes with wide, wraparound porches, a part of the city some would call "backbone" Washington.

There are pockets of black affluence, such as the Gold Coast, which hugs the east side of Rock Creek Park. Realtor Flaxie Pinkett, an institution in these circles, says she was encouraged shortly after Reagan's election by a dinner he held for several prominent area residents, including Mayor Marion Barry and his wife Effi.

"The fact that they had a dinner, with the mayor next to Mrs. Reagan and his wife next to the president-elect, meant something to me, and I guess it meant something to a lot of people in Washington," Pinkett said. "It meant that he was recognizing the elected officials of our city. I was terribly impressed."

Pinkett shares with many old-line Washingtonians a deep pride in her city and a social philosophy not far removed from that of the new president. "When you see all those people down at the White House picketing and carrying on, you don't see so many people from this city," she said. "Those are people from the hinterlands."

So this is not all alien territory Ronald Reagan is entering, by any means. There are even neighborhoods west of the park that are almost entirely Republican. Much of Washington believes in family, church, hard work and the other kitchen-sampler values that Reagan promises to restore.

The secular city, ranging from the thriving pornography district just blocks from the White House to the fast-paced world of high-priced drugs to the parts of town where brunch tables are more crowded during church on Sunday mornings than afterwards, has no reason to get in Reagan's way if he minds his own business.

But if he takes the time to get out and around, Reagan will not be able to escape the fact that parts of the nation's capital, like parts of virtually all of America's cities, are pure moonscape.

The ominous phrase "permanent underclass" has been bandied about recently to describe inhabitants of these inner-city war zones. Reagan must find a way to rehabilitate dying cities, and the only reminder he wil ever need of the urgency of the problem is a quick drive up 14th Street NW to about the intersection of V Street where Rev. Raymond B. Kemp, pastor of St. Paul & Augustine Church, ministers to society's outcasts on some of the District's most treacherous streets.

"What difference will Reagan make?" Kemp asked. "Hold on a minute." He yelled something over his shoulder, then returned to the phone. "I'm saying goodbye to a man who has scars in his neck from shooting heroin," he explained. Nothing out of the ordinary.

Kemp put down the telephone and fired questions at the visitors.

"Is the heroin out of your system? Have you got a girlfriend? Yeah, yeah, that's what you always say. Clean yourself up and get a job." The man, for whom Kemp had hope but not optimism, quietly left.

"On one level, presidents come and go," Kemp said, returning to the telephone. "On another, though, the mood in the street is that times are tough, and they're going to get tougher. Maybe we're ready to have things couched in Republican terminology.

Maybe we're ready to say it's time to work on ourselves for a while. I'm not sure that's half bad. Maybe it's time to say that the government isn't interested in giveaways but it is interested in helping people do bootstrapping things.

"Reagan has got to take care of Washington. No president wants an upset in his back yard. Every president has to take care of his own back yard, doesn't he?"