From the New York Times:
As gay rights advocates intensify their campaign to legalize same-sex marriage in New York, the bulk of their money is coming from an unexpected source: a group of conservative financiers and wealthy donors to the Republican Party, most of whom are known for bankrolling right-leaning candidates and causes.
... The donors represent some of New York’s wealthiest and most politically active figures and include Paul E. Singer, a hedge fund manager and top-tier Republican donor.
...The new donations represent roughly two-thirds of the same-sex marriage coalition’s fund-raising, making New York the rare state where a lobbying campaign in favor of legalizing gay unions is not being financed primarily by liberal donors and Democrats.
...Some of the donors were recruited by Ken Mehlman, a contributor to the coalition and a former chairman of the Republican National Committee, who has since announced that he is gay.