Marissen is also a director of Pacific Future Energy Corporation, along with former International Trade Minister Stockwell Day  and former National Chief of the Assembly of First Nations Shawn Atleo. Former National Chief Ovide Mercredi and Dave Coles, former President of the Canadian Communications, Energy and Paperworkers union (CEP), are also involved in the project.
Marissen graduated from Carleton University with a Bachelor of Arts in political science, and also attended Simon Fraser University. Marissen resides in Vancouver, British Columbia, and has one child (Hamish Marissen-Clark) by his ex-wife, the 35th British Columbia Premier Christy Clark. Marissen's older brother is professor of music Michael Marissen, who has taught at Princeton University, the University of Pennsylvania, and Swarthmore College.
Marissen has a long record of involvement in the Liberal Party, joining the party in early high school. Upon graduating from Carleton University, Marissen served as the party's national youth director in the early 1990s, and as an organizer for the Liberal national campaign during the 1993 federal election under then-leader Jean Chrétien. Subsequently, Marissen became a political advisor to then cabinet minister David Anderson during his tenures as Minister of National Revenue, Minister of Transport, and Minister of Fisheries and Oceans.
Marissen was the British Columbia campaign chair for Paul Martin's successful bid for the leadership of the Liberal Party of Canada and then served as the federal Liberals' British Columbia campaign co-chair in the 2004 and 2006 general elections.
In 2006 Marissen served as campaign manager for Stéphane Dion's successful campaign to become leader of the Liberal Party of Canada. It was a come-from-behind victory which many observers viewed as an historic upset. The vote took place at the 2006 leadership convention in Montreal on December 2, 2006.
Dion appointed Marissen, Nancy Girard and Senator David Smith as national campaign co-chairs for the Liberal campaign in the federal election which took place October 14, 2008. While no one predicted victory for the Liberal Party, and Prime Minister Harper was held to a second minority, Mr. Dion was widely criticized for his performance.
Following Dion's resignation, Marissen supported Michael Ignatieff for Liberal Party leader. Ignatieff was confirmed as Leader at a national convention in Vancouver in late April 2009. In the most recent federal Liberal leadership contest, Marissen was campaign manager for George Takach for Liberal Party leader. After Takach withdrew from the contest, Marissen joined him in supporting Justin Trudeau.
In July 2018, Mark helped to create YES Vancouver, a new "YIMBY" municipal political party devoted to solving Vancouver's housing crisis by focusing on building more supply. YES Vancouver ran candidates for council, school board and park board. Hector Bremner, a councillor for the Non Partisan Association of Vancouver, ran for Mayor under the YES banner, but only took 5.73% of the vote.
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