He was some time, before retiring in 1908, Acting Undersecretary for Defense. He was also vice-chairman of the Historical Section of the Wellington Philosophical Society. He was the author of a book on the East Coast Maori legends. He also completed a history of the Maori war with Te Kooti.
In 1878 he was elected mayor of Gisborne.[2] He was re-elected unopposed in 1879 and 1880.[3] He had intended to contest the East Coast electorate in the 1879 election but pulled out shortly before.[4] In 1880 he was challenged for the mayoralty by former mayor William Fitzgerald Crawford, and won by just three votes.[3][5] He retired the mayoralty in order to run for parliament in the 1881 election,[6] in which he placed third.[7] He returned to the mayoralty unopposed in 1883.[3] He retired again in 1884 and endorsed recently defeated MP Cecil de Lautour for the mayoralty.[8][9] He was elected mayor again in 1886 following the resignation of Allan McDonald.[10]
The day before his death on 12 November 1920, parliament had passed a bill to award Porter with a permanent pension of £200 a year.[11]