He joined the Green Party in 1991 when he was living in Boulder, Colorado, and was active at the local level initially. He first attended a national gathering in 1995, and in 1997 was elected Secretary of the new Association of State Green Parties, a post which he held until December 1999. Myerson coordinated the Green Party’s 2000 National Nominating Convention in Denver where Ralph Nader was nominated. 
Myerson worked on the national campaign staff for Ralph Nader's 2000 presidential bid for most of 2000, filling various roles, such as liaison to the Green Party, overseeing petition drives in Kansas and Wyoming, and later coordinating the campaign in eight inter-mountain and plains states surrounding Colorado.
In 2001, the new Green Party of the United States hired him to work on their application to the Federal Election Commission for national committee status, which was achieved in August 2001. In January 2002, Myerson moved from Boulder to Washington, DC, to open and manage the new GPUS office there, where he served as national Political Coordinator.
He left that position in September 2003 to take on the position of Executive Director of the Green Institute. Today Myerson serves as Executive Director of the Green Institute and Co- Director of the Green Institute’s GlobalPolicy360 project. Myerson is one member of the seven-member committee elected by the National Committee of the Green Party of the United States who serves on the Green Senatorial Campaign Committee (GSCC). He serves as the committees nonvoting treasurer. 
Myerson also was a member of the Boulder Green Alliance and the Green Party of Colorado during the 1990’s, and served various roles with the Greens there, including state party co-chair and candidate for the statewide office of University Regent. He also served on the Environmental Advisory Board in Boulder.