In April 2003, a team of journalism students taught by William Gaines conducted a detailed review of source materials, leading them to conclude that Fielding was Deep Throat, the unnamed source for articles written by Washington Post reporters Bob Woodward and Carl Bernstein. Many years previously, former White House Chief of Staff for Richard Nixon, H. R. Haldeman, also concluded that Fielding was Deep Throat. That speculation ended after former top Federal Bureau of Investigation official W. Mark Felt announced in May 2005 that he was the mysterious Watergate informant, as later confirmed by Woodward, Bernstein and Executive Editor Ben Bradlee in a statement released through The Washington Post.
He was selected on January 8, 2007 by President George W. Bush to replace outgoing White House Counsel Harriet Miers. Fielding was responsible for approving the pardon issued by President Bush to convicted real estate fraudster Isaac Toussie. When the New York Daily News reported that Toussie had made large contributions to the Republican Party, the White House revoked the pardon the next day.
Fielding has reportedly maintained close ties to Vice President Dick Cheney, whom he has known for decades and occasionally served as an informal adviser. However, according to Time magazine in July 2009, Fielding opposed Cheney's request that President Bush issue a full pardon to convicted vice presidential aide Scooter Libby. Following Fielding's advice, Bush ended up not pardoning Libby. J. Michael Luttig, a former federal judge who worked with Fielding in the Reagan Administration and remains close to Fielding, said: "He has a firm, clear view of executive prerogative, but he also understands as well as anyone in Washington the constitutional need for compromise. He is not someone that takes an absolutist position and then drives the presidency and the branches together off the brink. He has judgment."
Fielding serves on president-elect Donald Trump's legal team. Fielding's work for Trump was announced by his Morgan, Lewis colleague, Sheri Dillon, when she spoke at Trump's January 11, 2017, a day after a leaked document alleged the Trump campaign's long suspected collusion with Russian efforts to derail his presidential campaign competitor Hillary Clinton.
Fielding has published legal articles on the topics of presidential counsel and Russia and Ukraine matters in his role at Morgan, Lewis & Bockius LLP. The firm was named 2016 Russia Law Firm of the Year by Chambers and Partners The awards are based on research and, "substantial feedback from clients." The firm's Moscow office has won previous honors for its high-profile work in Russia. Including a Tier 1 rank from The Legal 500 EMEA for Corporate/M&A Law Firm, Russia and a rank in Bank 1 from Chambers Global for Energy & Natural Resources Law Firm, Russia.