WHEN YOU'RE running a circus, the point of the business is to get the customers excited, but not too excited. Once you've scared them with the elephants, show 'em to the egress before they burn down the house.

It's an axiom in Cambridge that the city council resembles nothing more than an erratic circus, and rent control is its most dependable elephant. In a city with a large number of renters who are well-organized by tenant and community groups, debates over control have been the council's most popular business for the last six years.

In 1969, tenants mobilized to get a referendum on control placed on the Cambridge ballot. They failed when the courts declared the referendum unconstitutional. They mobilized successfully in 1970, when Cambridge became the first city in Massachusetts to make use of the enabling legislation passed by the legislature permitting cities to institute controls.

In December, 1971, they organized when a lame duck council abolished controls. Under pressure, an incoming CCA majority re-instated the law in January, 1972.

This February, the crowds almost got out of hand. Control became an issue when independent councilor Thomas W. Danehy proposed abolition of the rent control board, the administrative arm of the control law. Danehy aimed merely to cause havoc on the council in order to break up the coalition between four liberals and two of the council's five independents that made independent Walter J. Sullivan mayor in February.

Danehy, a mayoral aspirant himself, was the big loser in that deal, and he hoped that rent control would cut into the coalition's unity. The four liberals on the coalition had all campaigned as strong supporters of the law, and the two independents, Sullivan and vice mayor Leonard Russell, were both on record opposing control.

Danehy's motion was immediately charter righted by Councilor Alfred E. Vellucci, an independent councilor and former mayor. The city charter gives each councilor the right to delay consideration of any motion brought before the council for one week.

DURING THE intervening week, while groups like Hard Times, the Cambridge Tenants Organizing Committee (CTOC), and Fight Back organized, the council factions lined up on the issue.

The four liberal councilors, elected on strong rent control platforms, with support from rich Brattle St., and poor neighborhoods like Cambridgeport/Riverside, came out for retention of the law, while four independents, with backing from areas of the city populated by homeowners, announced that they would vote for repeal.

The balance was held by self-styled populist Al Vellucci, who had supported control in the past. Vellucci loves to play to a crowd, or an issue. On the council floor, he will pace like a country lawyer, cross-examining witnesses and fellow councilors with a sarcasm tinged with ethnic pride. While the liberals complained about Danehy's attempt to split their coalition, Vellucci played coy, talking about the dilemma he faced deciding how to vote.

The tenants' groups mobilized 700 renters, who packed the city council meeting, filling the chamber and the gallery above and the stairs outside. Demonstrators struggled for the microphone, hooting at Sullivan and teasing him about his ambitions for the post of Sheriff of the country. The mayor directed the police restraining the crowd, calling each officer by his first name. "Are you still running for Sheriff, Sullivan?" someone shouted. "You bet I am!" he answered.

Under pressure from the crowd, the councilors huddled around the mayor's podium, and moved quickly to a vote. As expected, Vellucci voted for controls, and the council voted 5-4 to retain the law. The council agreed to hold a special meeting, on the next night, to give demonstrators a chance to air their grievances. Fewer than 100 demonstrators showed up, joined by only six councilors. The worst of the Danehy storm was avoided.

But it seems that the same pattern of challenge and response will continue far into the future. Tenants are currently organizing to put pressure on the state legislature, which is on the verge of refusing to renew the enabling for control, which expires next April.

As THE PROCESS goes on, the focus remains the same--the control law and its details--even though all groups involved in the struggle agree that control is an inadequate, and costly way to deal with the housing problem. Landlord groups, aiming for the end of all controls and a return to the free market, argue correctly that control acts like a lottery--benefiting those who are in the right place at the right time, not necessarily the poor, elderly or disadvantaged. At the same time, controls are a check on new construction, and may result in poor maintenance for some units.

Tenant groups admit that control does not solve the housing problem. CTOC holds that the solution to housing problems is the abolition of private property. CTOC spokesmen argue that control lowers rents for some tenants, and makes it harder for landlords to evict residents. Controls are also useful, according to CTOC, as a catalyst in tenant organization for more basic reform.

Writing in The Crimson five years ago, William Galeota called rent control a "panacea." He explained the 1969 turmoil about controls as a reaction to specific problems of the time--controversy over the proposed Inner Belt highway (since abandoned), the then-new NASA center, and the influx of people into the city.

If the 1969 turmoil did not solve the housing problem, Galeota wrote, "at least it has created an awareness on the part of the City government and other institutions, primarily the universities, that some action is required on housing." Five years has brought little action, and little alleviation of the problem.

In Cambridge, the show goes on. Rent control continues as a curious hybrid of emotion and uneasy compromise, more useful to politicians than to tenants. Housing grievances are channeled into debates and demonstrations about the control law and the administration of the control board. The political pageant of rent control is a diversion. And until a real solution is found, the circus will go on