He served in the Maine House of Representatives as the legislature's first member of the Green Party for two terms and was elected in 2002 and re-elected in 2004.

[4] Eder had previously supported Democrats while maintaining his Green voter registration, including future Portland Mayor Ethan Strimling.

He negotiated to have a dedicated staff person assigned to him, something individual legislators in the Maine House, who serve on a part-time basis, do not have.

In his first session Eder introduced legislation to give tax incentives for the purchase of alternative fuel vehicles, a bill to create a single-payer health care system in Maine and another to limit corporate power.

Two weeks later Eder deployed with the Red Cross to drive a food canteen truck and provide case management to victims of the storm.

A controversy erupted when Eder paid for an automated phone call to voters with a recorded message from the head of the local chapter of the National Organization for Women (NOW) endorsing Eder and questioning Hinck's position on women's rights based on Hinck's answers to NOW's candidate questionnaire.

[10] Former Eder campaign volunteers David A. Marshall and Kevin Donoghue took seats on the Portland City Council, becoming the first registered Greens to serve on that body.

Eder was the first member of a third-party to serve in the Maine Legislature since 1915 when representatives of Theodore Roosevelt's Progressive Party (United States) held legislative offices there.

[13] Eder travels the country speaking to regular citizens about to run and win local office as a way to demystify politics and feel empowered by taking personal responsibility for their own governance.

In the race Eder focused on providing living wages, affordable housing and health care for the city's working class residents.

[17] Upon making its endorsements in the mayor's race, the Portland Daily Sun said, "John Eder’s ideas surrounding affordable housing and public transportation (especially when it comes to replacing school buses with METRO passes) were apparently good enough to be incorporated by several opponents.