Prior to this he had taken a prominent part in political life, particularly interesting himself in the agitation for the separation of Port Phillip District from New South Wales.
He was a strong and earnest supporter of the anti-convict movement, and took a prominent part in the demonstration which was held in Melbourne in 1849, when the inhabitants resolved to oppose the landing of convicts from the ship Randolph by physical force, and to undergo any extremity of suffering rather than permit the colony to become a receptacle of felons.
[2] After separation had been secured, Mackinnon represented the Belfast and Warrnambool district in the old unicameral Victorian Legislative Council,[4] and assisted to pass a measure intended to prevent the introduction of convicted offenders into the colony.
[2] He energetically combated the efforts of the imperial authorities to prevent the effective administration of the enactment; and on the popular opposition proving successful he proceeded in 1853 with William Westgarth to Tasmania to assist the anti-transportation party in the colony.
[6] When the gold discoveries in Victoria gave such a wonderful impetus to the colony, the vigorous judgment and business ability of Mackinnon, with the brilliant literary qualities of his partner, Edward Wilson, placed the Argus in the van of the Australian press.