Dowd, a former Justice Department attorney, also investigated Pete Rose for Major League Baseball.
Also assisting Trump in handling the investigations is Jay Sekulow, chief counsel for the American Center for Law and Justice, a conservative advocacy group. Michael J. Bowe, an attorney with Kasowitz's law firm, is also assisting the team.
Trump faces multiple investigations into possible collusion between his campaign associates and Russian officials, who are said to have ordered an extensive effort to disrupt the 2016 election. A special counsel, led by former FBI director Robert S. Mueller III, is also looking into allegations that Trump attempted to obstruct the investigation, The Washington Post reported this week.
House and Senate investigators are also looking into Russian hacking and possible collusion of Trump campaign associates.