Daniel Stein, chief of the criminal division in the Manhattan U.S. attorney’s office, is departing to join the New York office of law firm Mayer Brown.  He will work in the firm’s global litigation practice.

Mr. Stein, who oversees more than 150 federal prosecutors, is the senior-most official to join the ranks of departing prosecutors from the Southern District of New York in recent months. His exit comes ahead of a U.S. presidential election that could shake up the leadership of the Justice Department.

Legal experts predict there could be increased turnover in the leadership ranks of the office and the Justice Department when a new president takes office in January, regardless of the election’s outcome. The next career move of Mr. Bharara himself is a source of constant speculation in the legal ranks

Mr. Stein first joined the Southern District in 2003, eventually becoming chief of the office’s public corruption unit before leaving in 2011. He came back to the office as chief counsel in 2014 after an overture from U.S. Attorney Preet Bharara.  Mr. Stein said that at Mayer Brown, he will focus his practice on counseling financial-services firms on regulatory enforcement, including securities enforcement, and government and internal investigations.