He was born in Cookstown, County Tyrone, to John Harbison, a general merchant, and Isabella Daly.
He became active in the Irish Parliamentary Party, acting from 1906 until 1910 as the election agent for William Redmond and Tom Kettle.
After attending the Irish Convention, he was elected to Westminster at the 1918 East Tyrone by-election, after Redmond resigned it to contest Waterford City.
Our liberties are gone; and if the younger men of Ireland become indignant, and take courses that no sane man could defend, who will be responsible?
The responsibility will be upon the men who have produced this Bill at the dictates of a narrow-minded set of reactionaries in the North-East corner of Ulster.