ALBANY – Six years before seeking to take on Eliot Spitzer in the New York governor’s race, William Weld went up against another New York City politician: Mayor Giuliani.

While Mr. Giuliani was trying to evict the Brooklyn Museum of Art from its premises for staging an exhibition that included a painting of the Virgin Mary embellished with clumps of elephant dung, Mr. Weld was pressing the case for the museum’s First Amendment rights to city officials.

Teaming up with First Amendment lawyer Floyd Abrams, Mr. Weld, a former governor of Massachusetts, worked on behalf of the embattled museum as a paid lobbyist.

“It was a First Amendment rights issue regarding the Brooklyn Institute of Arts and Sciences’ ability to hang whatever paintings they choose without interference from the government,” a spokeswoman for Mr. Weld’s campaign, Andrea Tantaros, said about the candidate’s work as a lobbyist for the museum.

Mr. Weld’s little-known role in the epic feud between the mayor and the Brooklyn Museum, a legal battle that turned into one of the most famous freedom of speech cases in recent years, sheds new light on the candidate’s work as a lawyer for the firm McDermott Will & Emery, where he dealt with private equity. It could open him to criticism from conservatives, especially Catholics, who sided with the mayor in the dispute.

The chairman of the Conservative Party of New York State, Michael Long, who has endorsed Republican candidate John Faso for governor, said that if Mr. Weld “wants to hold onto the premise that it was freedom of speech, I would hope he would agree that it was a vile expression of freedom of speech. It was a vile expression against Catholics.”

City records list Mr. Weld as being registered as a lobbyist for the Brooklyn Institute of Arts and Sciences, the legal name of the museum, between February 1 and December 31, 1999. He is one of three attorneys at the international law firm listed as lobbyists for the museum. The listed targets of the lobbying were the office of the mayor, the mayor, deputy mayors and staff, the Department of Cultural Affairs, and the Department of Design and Construction. Records show that Mr. Weld and the two other attorneys were lobbying on the subjects of budget funds and pass-through contracts between the city and the museum. The museum paid the firm $11,135 for its work.

Ms. Tantaros said Mr. Weld was “working” with Mr. Abrams, who represented the museum as a lawyer for the firm, Cahill Gordon & Reindel. Mr. Weld was not involved with the litigation.

Calling Chris Ofili’s painting of the Madonna “disgusting” and “sick,” Mr. Giuliani accused the museum of violating its lease and cut off its monthly funding of almost $500,000. The painting, titled “The Holy Virgin Mary,” also featured tiny photographs of buttocks and female genitalia.

While some defended the mayor for standing up for Catholics and for refusing to subsidize what Mr. Giuliani described as the desecration of someone else’s religion, others accused the mayor of censorship that was akin to punishing a public library for carrying an offensive book. In November 1999, a federal judge ruled against the city, and in March 2000 the city came to a settlement with the museum in which the city restored funding and the museum dropped its First Amendment lawsuit against the mayor.

Mr. Weld, who at the time was a new resident of New York City, left his job as managing partner of the New York branch of McDermott Will & Emery at the end of 2000.