washington former u.s. senator democratic vice presidential candidate joe lieberman withdraw consideration next director fbi cite potential appearance conflict interest give president donald trump decision retain attorney work firm lieberman work new york firm head marc kasowitz hire trump represent amid probe justice department congress possible tie trump 2016 presidential campaign russia selection marc kasowitz represent various investigations begin believe would best avoid appearance conflict interest lieberman write trump letter date wednesday copy letter first disclose wall street journal provide reuters thursday white house respond request comment lieberman withdrawal trump tell reporters week ago close select nominee replace jam comey director federal bureau investigation say lieberman lead candidate trump fire comey may decision set political firestorm give comey central role fbi probe russian meddle election potential collusion trump campaign associate russian officials seek swing vote trump favor department justice appoint special counsel former fbi director robert mueller lead independent investigation russia matter give kasowitz role lieberman might able participate russia investigation period two years without white house justice department waivers kathleen clark professor legal ethics washington university school law tell reuters wednesday federal regulation restrict newly hire government lawyers investigate prior law firm clients one year period extend two years executive order sign trump january cnn cite unnamed senior administration official report wednesday trump want renew search fbi director interview number candidates include lieberman thursday cite unnamed source cnn say john pistole former deputy director fbi former head transportation security administration consideration lieberman withdraw consideration fbi director