Mort Zuckerman told employees on Thursday that he is considering selling the New York Daily News, one of the city’s two tabloid newspapers and a virtual Big Apple institution. “A few weeks ago, we were approached about our potential interest in selling the Daily News. Although there were no immediate plans to consider a sale, we thought it would be prudent to explore the possibility,” the financial mogul wrote in an office memo. Zuckerman is a top conservative political donor. He is also the chairman and editor in chief of U.S. News & World Report. The News’s rival is the New York Post, which was purchased by Rupert Murdoch in the ’70s.