Ivan Zapien will leave his post as Chief of Staff to U.S. Senator Robert Menendez to accept a position in the private sector. He will be replaced by Danny O’Brien, who served as Chief of Staff to U.S. Senator Joseph Biden and as Political Director of Biden’s presidential campaign. O’Brien served as Chief of Staff to U.S. Senator Robert Torricelli, and was Co-Director of gubernatorial candidate James E. McGreevey’s coordinated campaign in 2001.