Former state Rep. Denise Harlow, a progressive who represented Portland and an elite marathoner who qualified in 2000 for the U.S. Olympic Trials, has died.

Harlow died Sunday from cancer, her sister, Kristen Harlow, confirmed Wednesday. She was 55, and had been living in Oquossoc, an unincorporated village near the town of Rangeley.

Harlow represented Portland in the Maine House of Representatives from 2010 to 2018, succeeding her father, the late Charles Harlow, who was also a former Portland mayor and city councilor.

She was most passionate about nature, and served on the Legislature’s committee dealing with the environment. She also sat on the inland fisheries and wildlife panel. Harlow and former state Rep. Ralph Chapman of Brooksville unenrolled from the Democratic Party in 2017 after splitting with most of their caucus to oppose a bill overhauling Maine’s metallic mining regulations.

Harlow, who served the remainder of her final term as an independent, said in 2017 that she remained “aligned with the core Democratic values” but added that “individual thinkers are often marginalized” in the party. She said she was “extremely concerned” about the influence lobbyists have in Augusta.

Harlow also introduced legislation in 2011 to recognize Juneteenth as a state holiday in Maine. She did so a decade before Congress made the day commemorating the emancipation of enslaved people in the U.S. a federal holiday.

Running was a big part of Harlow’s life, and she was fast, qualifying for the 2000 U.S. Olympic Trials in the marathon.

She taught middle school students at Maine Virtual Academy in the last few years of her life, with her sister describing how she “really loved her students” and that “they loved her.”

Ed Suslovic, a former state representative and Portland City Council member, recalled his friend’s “incredible sense of humor” and his “rivalry” with her over who had more campaign signs in yards when the two were running for office.

“She was tough as nails, and yet also very compassionate,” Suslovic said Thursday morning.

Harlow was “friends with everyone,” including those who opposed her progressive views, her sister added.

“She was just an incredibly funny, incredibly smart woman who was a big believer in justice, and who was completely authentic to what she believed,” Kristen Harlow said.