Now, Mr. Whitman—who for years plied his trade for the polling-industry titan Penn, Berland & Schoen—is turning his attention to a more local matter: He wants to see New York City Council Speaker Christine Quinn elected Mayor of New York in 2009.

“I think Christine shows extraordinary leadership, starting as a City Council member for my district,” said Mr. Whitman, who, like Ms. Quinn, is gay. “And not only for the gay community, but the city at large and for all New Yorkers.”

Next month, he is hosting a fund-raiser in his home on West 14th Street for—according to the invitation he wrote—“New York City Council Speaker and the next Mayor of New York, Christine Quinn.”

“My hope is that she will run, as I think she would make a fantastic Mayor, and I would do anything I could to help if she does,” he said.

Mr. Whitman’s only previous involvement on the money side of New York politics was in 2005, when he made a contribution to Brian Ellner, an unsuccessful candidate for Manhattan borough president.

But he has been moved to get involved in the upcoming Mayor’s race, he said, for a chance to make history.

“I think between Nancy Pelosi becoming Speaker of the House, and Hillary running as one of the top-tier candidates on either side—and then you have many other states where you have very strong women in positions of leadership, either Senators from Maine and Washington, or governors across the country,” he said. “And New York, in many respects, being the largest, and oftentimes being thought of as a progressive city—we’re behind the times.”