BACK IN the old days, when businessmen wanted to get something done in the District they didn't bother checking with the D.C. City Council. They simply rode the elevator up to the fifth floor of the District Building to cut a deal with the mayor or visited Capitol Hill to have a chat with a sympathetic subcommittee chairman with power over the city.

In those days few bothered with the City Council for one simple reason: The council made little difference. Before home rule the council had no power; and even after home rule began in 1975, it was largely a cheerleading section for liberal causes.

Today, things are different. The City Council matters. It has muscled its way into the real action at the center of city government. Any lobbyist worth his retainer now makes a point of letting council members know of his client's interest in pending bills; and special interests make sure that they have a lobbyist to represent them before the council. As a result, the number of lobbyists registered before the council has grown from 31 ten years ago to 130 today.

The transformation of the council mirrors the evolution of Washington, D.C., into a real city. This process carries obvious dangers. The council, in its move from knee-jerk liberal forum into a politically-charged body, now faces the same temptations that are evident in most city governments: pork-barrel politics, cronyism and jousting with the mayor. Although some may lament the change, it is yet another indication that Washington is coming of age, with the sort of political system -- and potential problems of corruption -- that are commonplace in most other big cities.

As in other big cities, political power attracts political money. Council members, sensing an opportunity for political aggrandizement, capitalize on interest groups with deep pockets to build up their campaign chests. With more money available, one inevitable result is that the cost of running a political campaign has mushroomed. In 1974, 12 candidates for four at-large council seats raised a total of $59,367 before the fall election. By comparison, one month before the September primary in 1984, two incumbent at-large candidates alone raised a total of $260,100.

The council's emergence as a political force has been especially pronounced in the past two or three years as it discovered that it had much to offer to groups and individuals seeking to move the course of government. True, the mayor runs the city bureaucracy and parcels out contracts. But the council has extraordinary power to shape the local economy and bestow financial rewards on those who play ball with it.

It was the City Council, for example, not Marion Barry, that awarded the multimillion dollar cable television franchise last year; the City Council approved the $654 million in tax-free revenue bonds for corporations and non-profit groups in the past five years; it was the City Council that took pity on local hotel owners who complained about rising property assessments and gave them a big tax break last year; and it's the City Council that has the power to make or break a bank merger

The new City Council rejects the rubber stamp label the media used to hang on it. Marion Barry is a more political mayor than his predecessor, and the council has risen to the challenge, keeping Barry off balance. The council demanded and won a role in settling a simmering contract dispute with police officers. It forced the city's Housing Finance Agency, whose members had been appointed by Barry, to come to the council for approval before issuing housing bonds. It upstaged Barry recently by adding funds to the mayor's 1987 budget for public schools. And it overrode three consecutive mayoral vetoes between December 1984 and October 1985.

"We're no longer the student council," said council member John Wilson (D-Ward 2). "We're a legislative body that knows how to deal with its role . . . I don't think the council will ever again turn back into a wimp."

The first elected City Council, which took office in 1975, was largely a collection of civil rights activists, community organizers and liberal social reformers whose agenda of rent control, increased welfare benefits and sharing power and economic benefits with the poor didn't sit well with the Greater Washington Board of Trade set.

There were some pro-business sympathies even then. Sterling Tucker, a former Washington Urban League executive and the first elected council chairman, lent a sympathetic ear to the business community; Marion Barry, a former civil rights activist who was then chairman of the council's finance and revenue committee, fought a proposal to impose a gross receipts tax on businesses.

But it was council member Douglas Moore, chairman of the old budget committee, who exemplified the rampant anti-business sentiment within the council.

Moore, a controversial minister who once bit a tow truck driver, derided the proposal to build the D.C. Convention Center as "a huge public works welfare give-away for the business community" and advocated legislation prohibiting the Redskins from selling season's tickets because the lion's share went to corporations and suburbanites.

John Tydings, executive director of the Greater Washington Board of Trade, recalls that businessmen often dreaded having to deal with the council because of the overt hostility. "I always felt that there was a sense of, 'You owe us . . . for years of opposing home rule and should work with us on anything we do."

In those days, the council crusaded to maintain affordable rental housing for the poor by extending the rent control law and placing restrictions on the conversion of apartments to condominiums and cooperatives. The council also adopted a pioneering minority contracting program that set aside 25 percent of all city contracts for minority firms that previously had been shut out.

The makeup of the council has changed substantially since then. Only five of the original 13 members are still in office and one of them, Polly Shackleton (D-Ward 3), whose liberal credentials are rooted in the New Deal, will retire at the end of the year.

The council's agenda has changed as well. In the past 14 months, the council has opened the District to interstate banking, voted to gut the city's two-year-old no-fault auto insurance program at the behest of trial lawyers, and voted to increase the number of housing units exempt from the city's long standing rent control program -- hardly the handiwork of a band of knee-jerk liberals.

Tenants and labor groups were so enraged by the council's action in eliminating certain rent controls that they waged and won the first referendum campaign in the city's history to delete provisions from a law passed by their elected leaders.

Council members insist they are even-handed in balancing the interests of their constituents and consumers with those of the business community, and that in the long run everyone will benefit from the city's efforts to spur economic development. In fact, the council, which once prided itself as the champion of the "little man" and the poor, has become decidedly more conservative and pro-business.

"I think there's a new realism in the attitude toward the business community," said council member Charlene Drew Jarvis (D-Ward 4), chairman of the housing and economic development committee, in explaining the striking new pro-business attitude of many of the council members. "My own attitude is that in the past we thought being pro-business was being anti-consumer. I've tried to steer away from that."

In looking at District politics, it's easy to forget that home rule government has been at work for little more than a decade and still is in the formative stages. The fear that Congress would continue to dominate local government never materialized, although Congress twice has stricken legislation approved by the City Council and has pressured the District officials to build a new prison.

The Democrats have dominated the council from the start and today hold an 11 to 2 advantage, and yet they have been unwilling or incapable of forging a political consensus. Tucker had modest success in putting together a working majority. Arrington Dixon, Tucker's successor, rarely could put together a key vote. David A. Clarke, the current chairman, says he prefers the role of mediator and frequently defers to the chairmen of the council's 10 standing committees.

Two things have happened as a result: Much of the power of the council has been ceded to committee chairmen. And in many cases where the council is badly divided, a single council member can determine the outcome of a crucial vote.

Jarvis, as chairman of the housing and economic development committee, took the lead in redrafting the regional banking legislation and signs off on every city funded redevelopment project in which private developers seek seed money from the government. Wilson, chairman of the finance and revenue committee, controls all tax legislation that flows through the council and must approve all applications for tax-exempt industrial revenue bonds. Council member John Ray (D-At-Large), chairman of the consumer and regulatory affairs committee, was a prime mover in killing off the no-fault auto insurance program.

The battles last year over no-fault, cable TV and rent control illustrate the enormous power that an individual member holds on a council with constantly shifting alliances.

Council member Nadine P. Winter (D-Ward 6) was for years a staunch supporter of the city's rent control laws and voted three years ago to institute a no-fault auto insurance program as a means of holding down insurance costs. Last year, under intense lobbying, she flip-flopped and cast crucial votes to eliminate some of the rent controls and to kill off no-fault.

The surge in lobbying of the City Council bespeaks the vast profits frequently at stake. For instance, enactment of the interstate banking legislation sets the stage for future bank mergers and buyouts and clearly has enhanced the stock value of existing banks. Since December 1984, the total market value of all stock for American Security Bank increased from $195 million to $379 million; the market value of Riggs National Bank rose from $199 million to $401 million, according to Eliot H. Benson, a vice president and research director of Ferris & Co. Benson said the dramatic increases in value in part "reflect the development on the legislative front."

In some cases, the immediate economic impact of D.C. legislation is less important to industry than the precedent it sets in dealing with other legislatures around the country.

"It's the nation's capital, so the issue sometimes is more symbolic than big bucks," said Lawrence Mirel, a former legal counsel to the City Council and now a local lobbyist. "If you do something here, it gets written up in The Washington Post and everyone knows about it," he said. "If you do something in Idaho, who the hell knows about it?"

Mirel and other lobbyists acknowledge that the City Council has come of age. Lobbyists who ignore the concerns of individual members or who try to get things done the old way, usually run into trouble. The battle over the interstate banking law is a case in point.

Barry, anxious for the city to get in step with national trends toward regional banking, introduced a banking bill to the council last year. The bill included no provisions that would have allowed banking giants like Citicorp of New York, with home offices outside the region, to move into the Washington market. Citicorp executives were eager to expand into this market and decided to deal directly with the mayor to get amendments introduced that would pave the way for Citicorp's entry. As a sweetener, Citicorp picked picked up the $40,000 tab for a city-sponsored Chinese trade show that the mayor had helped to organize and offered to provide up to $100 million in loans and credit to depressed areas of the city in exchange for banking privileges.

Citicorp was stunned when the council rejected the amendments introduced by Barry and rejoiced when the mayor vetoed the bill as being inadequate. The council responded by overriding the veto. At that point, Citicorp had no choice but to shift its focus to the council and try to offset the lobbying efforts of local banking officials, who didn't want Citicorp entering the market.

Citicorp vice president Lucius P. Gregg invited council members literally to prepare a "shopping list" of projects in their wards that could benefit from Citicorp loans.

In the end, Citicorp got much of what it wanted -- amendments to the legislation that will enable the money center to move into the area and perhaps start buying up banks. But the city also benefitted from the council's holding the bank's feet to the fire: The legislation requires that in order to acquire a D.C. bank, Citicorp must provide up to $100 million in loans and lines of credit for economic development projects in distressed areas of the city and create up to 200 new jobs for District residents.