President Barack Obama announced Thursday that Attorney General Eric Holder will resign after six years in office.

Holder, the first African American to hold the office, has said he will stay on until the approval of a replacement. Holder has been a controversial figure on both sides of the political aisle, and gaining Congressional approval for his replacement may prove difficult for the President, especially in an election year.

Potential nominees include former white house counselor Katheryn Ruemmler; Mass. Gov. Deval Patrick; Solicitor General Donald B. Verrilli Jr.; former Mich. Gov. Jennifer M. Granholme; Senator Sheldon Whitehouse of Rhode Island; U.S. attorney Preet Bharara of New York; and U.S. attorney Loretta E. Lynch, also of New York.