He has served in city government, rising to the position of director of the Philadelphia Youth Commission.

Since his election to the Pennsylvania House of Representatives in 2012, Harris has advocated for criminal justice reform, supporting clean slate bills to allow people convicted of felonies to, after a certain amount of time, have their conviction removed from their record.

[2] Harris worked on this legislation since he was sworn into office, and Governor Tom Wolf signed the Clean Slate Act in June 2018.

[2] Harris was selected by the Pennsylvania Democratic Party as one of 20 delegates to the United States Electoral College for Joe Biden and his running mate, Kamala Harris, in the 2020 United States presidential election.

In May 2023, Harris, along with fellow Philadelphia-area Representative Jared Solomon, established the legislative Black-Jewish Caucus.