Even though the Maine Green Party has been one of the strongest state units of the Green Party for many years, the party has never had a nominee for either branch of Congress. On November 24, Henry John Bear, one of the two Green state legislators, announced his candidacy for the 2nd district in 2018. See this story.
If the petition currently circulating for ranked choice voting succeeds, and if the voters again vote in favor of that system in June 2018, then Maine will use ranked choice voting for congressional elections in 2018.
Maine is the only state with any tribal representatives to the state legislature. The three tribal representatives represent, respectively, the Passamaquoddy, Penobscot, and Maliseet people. The tribes select them by their own process. They can introduce bills and participate in the committee process, but do not cast a vote on the floor.
On Tuesday, Representative Henry John Bear of the Maliseets changed his registration from Democratic to Green. He had sought election to a regular position in 2016 from district 144, and had won the Democratic nomination, but then he had withdrawn from that public election. He has been the Maliseet representative since 2012. Thanks to Joshua H. for this news.