Tenants, community activists and members of the Congressional Black Caucus waged an intense, last-minute campaign yesterday to persuade the D.C. City Council to change its mind and reject rent control legislation that would give landlords the right to higher rent increases and exempt more properties from controls.

Supporters of the legislation, including council member John Ray (D-At Large), predicted the bill would survive its final test at a City Council meeting tonight. However, a section that would exempt single-family homes from rent controls as they became vacant may be amended to apply only to houses owned by individuals and not corporations or conglomerates.

"Other than some technical amendments, I don't see any major amendments being made," Ray said. "Certainly, those of us who have gotten things so far along would oppose anything of a substantial nature."

The legislation was initially pushed through the council by a seven-member majority on April 16. The main targets of yesterday's lobbying were council members William Spaulding (D-Ward 5) and Nadine P. Winter (D-Ward 6), whose support of the legislation was viewed by some as tenuous.

Spaulding, who was booed by an angry gathering of 170 persons in Ward 5 last Wednesday, appeared nervous and tense yesterday as he told a reporter he had not decided whether to continue to support the bill. "My mind is still open," he said. "I'm still assessing."

Winter said she will vote for final passage of the bill tonight, despite mounting pressure from tenant groups, advisory neighborhood commissioners and Democratic activists in her ward. However, she said she would support the amendment that would keep some single-family rental units under controls. "I think it's a good bill, despite all of the hullabaloo."

Under the bill tentatively approved by the City Council, landlords would be permitted 12 percent rent increases on vacant units instead of the current 10 percent. Landlords filing hardship petitions would be permitted a 12 percent rate of return on their properties instead of the current 10 percent, while regular automatic increases would still be tied to the metropolitan consumer price index and limited to 10 percent.

On a case-by-case basis, rent controls would be lifted on buildings 80 percent or more vacant. And beginning in 1989, apartments would become exempt from rent control as they become vacant, provided the District's vacancy rate is at least 6 percent and a tenant subsidy fund has been established.

About 40 members of the Emergency Committee to Save Rental Housing demonstrated against the bill outside the District Building late yesterday afternoon, while 12 members of the Congressional Black Caucus wrote a letter to Council Chairman David A. Clarke expressing strong support for extension of the current rent control law.

"Given the severe housing crisis that exists throughout the country, including D.C., which is compounded by the administration's continued reduction in assistance for low-income housing, we find it highly distressing that the bill would have the support of most council members," the letter stated.

Clarke, who failed to win support for his bill to extend the current rent control legislation, met with Spaulding and Winter yesterday in hopes of changing their minds.

Winter, who is up for reelection next year and may face a tough challenge from former D.C. Democratic state party chairman Theodis (Ted) Gay, said that Clarke warned her, "Nadine, you've got political problems if you don't go with me."

Winter defended the bill as one that would effectively continue rent controls because it is unlikely that the city's vacancy rate will ever reach 6 percent, and she said that it would help to place boarded-up single-family houses back on the market to provide housing for middle-income residents.

She said that Clarke would concede these points if he were being completely honest, but that he is more concerned at this point in "trying to save face politically."

Clarke declined to comment on his conversation with Winter, although he said that the current bill is better than the one originally introduced by Ray.

As for the possibility of the vacancy rate reaching 6 percent and triggering rent decontrol, as some tenants fear, Clarke said: "I will say it may not occur. I don't know whether it will occur."