About two weeks after Paul Manafort Jr. swapped his lawyers from Wilmer Cutler Pickering Hale and Dorr for Miller & Chevalier, the former campaign manager for President Donald Trump saw another change in his legal representation.

Kevin Downing, a Miller & Chevalier partner advising Manafort in the U.S. Department of Justice's investigation into alleged links between the Trump campaign and Russia, left the firm Thursday.

We conducted a conflicts check and analysis, the firm said Friday through an outside spokeswoman. We subsequently determined that an existing client matter prevents the firm from representing Mr. Manafort at this time.

Downing decided to leave the firm so that he can represent Mr. Manafort, the firm said. Kevin is an exceptional lawyer who will serve Mr. Manafort well. We wish him the very best.

The Associated Press first reported Friday on the departure of Downing (pictured right) from Miller & Chevalier, a firm he joined in June 2012 after serving as a senior litigation counsel in the Justice Department's tax division.

Manafort previously dropped his counsel Reginald Brown at Wilmer and brought in Miller & Chevalier on Aug. 10. At the time, Manafort's spokesman did not give a reason for the change.

Manafort himself appears to be one of several individuals under investigation by Justice Department special counsel Robert Mueller III's probe of the Trump campaign. In late July, the FBI searched Manafort's home in Alexandria, Virginia, seeking tax and banking documents.

NBC News reported late Friday that the Mueller investigation had subpoenaed documents and testimony from companies that worked on an international public relations campaign orchestrated by Manafort. The work by Manafort and Mercury Public Affairs, noted by The American Lawyer earlier this year, is related to a group called the European Center for a Modern Ukraine. ABC News reported Friday that people linked to Michael Flynn, the Trump administration's former national security adviser, had also received subpoenas.

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The mounting legal work resulting from Mueller's Russia probe has been a boon to white-collar lawyers in the nation's capital. Manafort's recent switch from Wilmer to Miller & Chevalier could mean several different things.

Manafort's legal bills could cost less at a smaller firm like Miller & Chevalier. His legal defense could require the tax expertise typically provided by those in Miller & Chevalier's partnership. Manafort may have also wanted to avoid the appearance of a conflict of interest between his former lawyersand Mueller, a former Wilmer partner. A true conflict of interest, however, never materialized between Wilmer and Mueller's team, which has several ex-Wilmer partners.

Miller & Chevalier and Manafort have long had close ties. When the Russia matter first arose, Manafort relied on his longtime lawyer Richard Hibey, then a partner at the firm. Hibey even accompanied Manafort to a Senate Intelligence Committee hearing in July.

Hibey retired from Miller & Chevalier earlier this summer, said the firm's spokeswoman.

Generally, Milller & Chevalier is known for its work on tax matters and on international law issues and litigation. The firm's only office is in Washington, D.C., and its foreign clients in the past have included the governments of Singapore and Taiwan, according to records on file with the Justice Department.

Only two other partners have left Miller & Chevalier so far this year, both for in-house jobs outside of Washington, D.C. The firm transitioned its chairmanship in June from Anthony Shelley to tax policy specialist Marc Gerson.

Hibey and Downing could not be reached for comment Friday. A spokesman for Manafort did not return a request for comment about his client's outside counsel.

Downing is still listed with The District of Columbia Bar as part of Miller & Chevalier, although his biography page was removed from the firm's website Friday. While corporate client and litigation conflicts often arise in Big Law, it's unusual for a lawyer to leave his firm to keep representing an individual.

In a similarly politicized situation, former U.S. Solicitor General Paul Clement publicly split with King & Spalding in 2011 and joined Washington, D.C.-based litigation boutique Bancroft due to his representation of the Republican-held House of Representatives in a court fight over same-sex marriage. Kirkland & Ellis acquired Bancroft last year.

Katelyn Polantz is based in Washington, D.C., and writes about government and the business of law. She can be reached at kpolantz@alm.com. On Twitter: @kpolantz