 Complete the following phrase:  Following the Clinton administration, he worked at the law firm of Covington  Burling in Washington, D.C., representing the firms multinational corporate clients in litigation. He was senior legal advisor to Barack Obama during Obamas presidential campaign and one of three members of Obamas vice-presidential selection committee. Holder was a close ally and confidant of Obamas and was selected as President Obamas first Attorney General. Although he became the first sitting Attorney General to be held in contempt of Congress during an investigation of the Operation Fast and Furious 