Blaney, a native of Fanad in the north of County Donegal, had been a commander of the Irish Republican Army in Donegal during the War of Independence and the Civil War. He was first elected as a Teachta Dála (TD) to the 5th Dáil for the Donegal constituency at the June 1927 general election. He retained his seat at subsequent general elections until it was abolished in boundary changes for the 1937 general election when he was returned for the new Donegal East constituency. He lost his seat at the 1938 general election, and was elected to the 3rd Seanad on the Agricultural Panel, serving until 1943.