Housing Activist Margarita Lopez’s hairs-breadth upset of Sheldon Silver aide Judy Rapvogel in the Democratic primary for the Lower East Side’s City Council–certified last week–was largely the product of tenant organizing.

Rapvogel had been widely expected to win. With help from the Assembly Speaker, she had drawn endorsements from such key Democratic players as Ruth Messinger and local 1199. But Lopez, with the help of 450 volunteers and thousands of new voters registered in the scores of housing projects banked along the East River, took the nomination by 210 votes out of almost 15,000 cast–after Rapvogel had been named the winner on primary day.

“We showed the Democratic party that if you deal with the issues, you can go up against Goliath,” says district leader Armando Perez, a Lopez supporter.

Lopez says that affordable housing was her number-one issue-and it resonated with Lower East Side voters. In the last four years, rents for vacant apartments in the area almost doubled, and tenants in place have been threatened with attempts to deregulate public housing and dismantle rent controls. In the area east of Third Avenue between Delancey and East 14th streets, she won 70 percent of the vote.

“My record on housing is well known,” she says. She was one of the main organizers who mobilized against Long Island Congressman Rick Lazio’s attempt to deregulate public housing last year, as well as similar moves by the Giuliani administration.

In the process, according to Perez, they registered at least 4,000 new voters since 1994. Rapvogel, who had trouble wooing public housing tenants, appealed to tenants in other parts of the district, linking herself to Silver’s role in preventing the total decimation of the state’s rent-regulation laws.

If elected in November, Lopez will replace Antonio Pagan, who won in 1991 and 1993 with a coalition of Latinos, young professionals and landlords but alienated many in the neighborhood with his vituperative, combative style. Judy Rapvogel could not be reached for comment. She will be on the Liberal Party line in November.