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. Marissen was very involved in BC Premier Christy Clark's successful campaign in the 2013 BC provincial election. More recently, Marissen served as strategist for Michael Lee's campaign for the leadership of the BC Liberal Party, where Mr. Lee was 30 points short from being on the final ballot. 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 zoning reform. 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.
