Robert Mueller could face one significant issue with his appointment as special counsel to lead the Justice Department's investigation into ties between Russia and Donald Trump's presidential campaign: the law firm he's worked at since 2014 has represented several prominent players in President Donald Trump bid for the White House.Former Trump campaign chairman Paul Manafort, Trump's daughter Ivanka and his son-in-law Jared Kushner are all clients of Wilmer Hale, the firm Mueller is leaving to assume the position of special prosecutor overseeing the high-profile Russia election probe.One prominent expert on government ethics rules said Wednesday that lawyers entering federal service would normally be required to recuse themselves from decisions regarding individuals who were represented by the new official's former firm."It's a possible wrinkle in all off this," said Richard Painter, a University of Minnesota law professor and former White House ethics lawyer under President George W.