Libby served on the Lewiston city council from 2011-2015 and has chaired Lewiston’s Universally Accessible Playground committee since 2016. He was elected to the Maine House of Representatives in 2012 and represented District 73 (now District 60) for two years. On Friday, February 14, 2014, Libby announced he would seek the District 21 Senate seat held by
Margaret Craven, who had just announced she would not seek re-election. In November 2014, he beat Republican Patti Gagne by less than 100 votes. Libby ran unopposed in the 2016 Democratic primary, the 2016 general election and the 2018 Democratic primary. In the 2018 general election, he beat Republican Nelson Peters Jr. 60%-40%, and his Democratic peers unanimously elected him Senate majority leader. November 2020, Libby was again selected as Senate majority leader. In early 2021, citing increasing professional and family obligations, Libby resigned his leadership position but remained in the District 21 seat.. Libby has served on the Government Oversight Committee, the Taxation Committee and the State and Local Government Committee. In July 2021, after Lewiston City Councilor
Safiya Khalid alleged racism at a meeting of the Lewiston Democratic Party, Libby dismissed her complaints and suggested Khalid's opponents were not racist. ==Personal life==