[1] A native of Cloncurry, he was raised in Prosperous, County Kildare by his aunt Elizabeth Tierney.
Taking the anti Treaty side in the Irish Civil War, Harris was captured by National forces on 27 June 1922 (the night before the Four Courts attack) but escaped from Newbridge Camp, County Kildare in October 1922.
He resumed active service but resigned from his position as Brigade Commandant in February 1923.
[3] A farmer, Harris was first elected to the Kildare constituency in a by-election in June 1931 caused by the death of Labour Party TD, Hugh Colohan.
With just over 40% of the vote Harris defeated Cumann na nGaedheal candidate John Curton and future Labour Party leader, William Norton.