Boycott Plan at Park Slope Food Co-op Draws Politicians" Opposition Michael Rieman, center, handed out fliers opposing a boycott of Israeli products by the Park Slope Food Co-op. A vote on whether to hold a referendum on the boycott is expected Tuesday. Many of New York City's leading politicians said Monday that they opposed a boycott of Israeli products by the Park Slope Food Co-op in Brooklyn, speaking out on the day before the market is expected to hold an initial vote on the proposal. Christine C. Quinn, the City Council speaker, called the idea "ill conceived." Bill de Blasio, the public advocate, said it was "madness." Scott M. Stringer, the Manhattan borough president, described the proposal as "an anti-Semitic crusade." Asked about the issue at a news conference in Brooklyn, Mayor Michael R. Bloomberg called Israel a close financial and political ally and said he wondered why the co-op would conduct a foreign policy debate. "Why any of this has anything to do with selling food, I don't know," Mr. Bloomberg said. The mayor said he would encourage New Yorkers to do more business with Israel, not less, and noted that Israel itself had been formed after a vote at the United Nations, then in Flushing, Queens. "I think it has nothing to do with the food," he said of the boycott. The issue is there are people who want Israel to be torn apart and everybody to be massacred, and America is not going to let that happen. The proposed boycott, an outgrowth of an international movement that pushes for divestment and sanctions against Israel, has pitted neighbor against neighbor at the 39-year-old co-op, a Brooklyn institution known for its organic produce and its socially conscious membership. Co-op members are scheduled to vote on Tuesday on whether to hold a referendum on the boycott. The boycott would be largely symbolic, because the co-op carries only a half-dozen or so products imported from Israel, including paprika, olive pesto and vegan marshmallows. But the debate has been divisive, and is taking place in an affluent neighborhood with an energized, highly active constituency that turns out in droves for local and citywide elections. "It's my home turf," Mr. de Blasio, a longtime Park Slope resident and likely mayoral candidate in 2013, said in a phone interview on Monday. His office had issued a written denunciation of the plan over the weekend. "I really have a lot of respect for the co-op and its history, and maybe that's in part what's motivating me," said Mr. de Blasio, who is not a current co-op member. I'm pained that an organization that has done so much good would wade into these waters. Unlike Mr. de Blasio, Ms. Quinn has not issued a formal statement regarding the vote on Tuesday. But the speaker, who is also planning a run for mayor, quickly responded to a reporter's inquiry on Monday and spoke at length about her own experiences visiting Israel, including a trip in 2007, when a rocket attack occurred nearby. "The relationship between New York and Israel, in my opinion, is very, very significant, and something I feel very, very strongly about," Ms. Quinn said. This boycott is ill conceived. I don't think there should be a vote, and I hope that is what happens. Asked for his view, Mr. Stringer, another likely mayoral candidate, issued a fierce denunciation, writing in an e-mail that the co-op "should not be torn apart" by a proposal he deemed anti-Semitic. "This action is an unwarranted attack on one of America's strongest allies and an embarrassment to our city," he wrote. Israeli politics is a topic close to the heart of the city's sprawling Jewish population, a group that has proven decisive in several high-profile political races in Brooklyn and Queens in recent months. "New York's neighborhoods have their own foreign policy," said Mitchell L. Moss, a professor of urban policy and planning at New York University, who added that the inclination of New Yorkers to weigh in on world events can have political implications for local elections. "The boundaries of New York's mayoral campaigns are infinite," Professor Moss said. Everything is potentially an issue.