He entered provincial politics and was elected as the fourth Superintendent of the Otago Province.

In 1858, he was appointed judge at the District Court and he held that position until 1862 when the office was abolished.

He had extensive holdings in Waihola, Otokia (south-west of Mosgiel), Lee Stream (inland from Outram), and West Taieri.

In the first council (1853–1855), he was a member of the Dunedin Country electorate and represented the interests of Port Chalmers.

[12] He claimed significant differences in opinion with his executive, as well as a need to devote more time to his private financial affairs, as reasons for his resignation.

Harris, James Turner, Thomas Birch and John Millar received 340, 273, 200 and 101 votes, respectively.

During his second term from 1867 to 1868, he was a member of the second Stafford Ministry (from 9 September 1867), holding the role of Solicitor-General from 26 October 1867 until 13 May 1868.

According to Bernard Foster, if it had not been for his financial difficulties, Harris "would probably have played an even more important part in provincial and colonial politics".