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Marcus Sebastian Mason

Senior Partner

Marcus Sebastian Mason joined The Madison Group in 2007. In his capacity as Senior Partner, Marcus is responsible for managing the firm’s tech, transportation, energy, tax, and homeland security portfolio, as well as the firm’s West Coast operation in California. His client work focuses on crisis management, complex integrated campaigns, and coalition building. His clients have included Fortune 500 companies like Avanir Pharmaceuticals, Avaya Communications, BNSF Railways, Cognizant Technologies, Energy Future Holdings, Google, and Intuit.


Prior to joining The Madison Group Marcus served as Amtrak's Senior Director of Government Affairs and its interim Head of Office. He was responsible for advancing the company's strategic business initiatives in the House of Representatives, United States Senate, and more than three dozen states. Prior to his tenure at Amtrak, Marcus served as both Chief of Staff and Legislative Director for two California Members of Congress. During that time, he initiated and had enacted several initiatives that impacted the 37th Congressional District and the State of California. Marcus managed a winning congressional campaign at age twenty-one before beginning his tenure as Capitol Hill's youngest Chief of Staff. 


Marcus served as an advisor to both campaigns of President Barack Obama and continued in that role during the two Administrations. He also served as a member of the Democratic National Committee and cycled off the board of directors of the Congressional Black Caucus Foundation (CBCF) where he served as Treasurer and chaired its Budget & Investment Committee. Currently, Marcus is on the board of directors of the Congressional Black Caucus Political Action Committee (CBC-PAC) and serves as treasurer for Protecting Our Vote PAC, a CBC backed super PAC that focuses on African American voter turnout which helped secure a Democratic Majority in the 2018 elections. He is also the president of the African-American lobbyists association, the Washington Government Relations Group (WGRG). 


Marcus is also a published author who writes spy thrillers under the pen name Sebastian Cheney. He is married to Christina Mary and is the father of three, Taelor Chanel, Romelo, and Grace Anne.

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1030 15th St. NW
Suite 1080 West
Washington, DC 20005

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Tel : 202.296.8686 / Fax : 202.296.3323