He was born into poverty, the third son of Patrick Power from Ballinasloe and his wife Mary O'Connor of County Roscommon, during the Potato Famine years, and was raised partly in the workhouse in Ballinasloe, County Galway, where he contacted smallpox, which left him facially scarred. He joined relatives in Lancashire when aged about fifteen, where he took up a trade in house painting. It was here that he first met Michael Davitt.
He embraced Fenianism, and became known to the police under alias names 'John Fleming', 'John Webster', 'Charles Ferguson'. After being involved in the abortive raid on Chester Castle in February 1867, he evaded capture and was sent to the United States later that year at the age of 21 to discuss reorganization of the Fenians. After his return he was arrested in Dublin on February 17 1868 and spent five months in Kilmainham and Mountjoy jails.
He was a member of the Irish Republican Brotherhood (IRB) Supreme Council and was believed to be involved in gun-running (a matter on which in later life he threatened legal action). While he remained an active member during his early years in Parliament, as early as 1868–69 he had promoted cooperation with constitutional politicians such as George Henry Moore.
In the 1874 Parliament, dominated by Disraeli's Conservatives, Isaac Butt's policy of attempting to achieve Irish nationalist objectives by working with the Liberals and Conservatives and respecting House traditions, failed; the Irish minority was simply ignored.
O'Connor Power and J.G. Biggar therefore pioneered the new policy of obstructionism, whereby House of Commons business was obstructed by making long speeches and manipulating its procedures. They were joined in this more successful policy by Charles Stewart Parnell on his election in April 1875.
O'Connor Power spoke strongly and repeatedly in Parliament from 1874 to 1877 for amnesty for Michael Davitt, imprisoned in Dartmoor, and other fenian prisoners, and brought to notice perceived unfairness of their treatment as common criminals rather than as political prisoners. This led to Gladstone lending his support to Fenian amnesty. Davitt was released early on December 19 1877, and Fenians Thomas Chambers, Charles McCarthy and John Patrick O'Brien followed in January 1878.
In 1876 O'Connor Power and Parnell were sent to the United States by the Home Rule League to congratulate the President Ulysses S. Grant on the American Centennial. At an informal meeting with the President, they asked that Ireland's bid for independence be given recognition. Power presented an address to the House of Representatives and on March 4 1877 the House passed a unanimous resolution recognising the services rendered by Irishmen to the United States and concluded that the principles of self-government be established as a sacred heritage to all future generations. He also used the American visit to resume contact with nationalist supporters, and is almost certainly the IRB agent referred to 'Shields'. O'Connor Power is perhaps best known for his work in the radical wing of the Home Rule League and support for tenant farmers' rights, on which he spoke forcefully in Parliament, in conjunction with Parnell, Michael Davitt, Matt Harris and James Daly.
He was generally considered by the Fenians to have sold-out to constitutionalism during his career. Along with J. G. Biggar he was expelled from the IRB Supreme Council in 1876. The Fenians of the "New Departure" refused to work with him and it was Parnell who become the man to bridge the gap between the Fenians and constitutionalists.
T. D. Sullivan presents an anecdote from 1876 that illustrates the distance that grew between O'Connor Power in his Home Rule days and some of his former radical nationalist colleagues:
An immense mass of people assembled in the Free Trade Hall [Manchester] on the 16 September 1876, to hear a lecture from Mr. John O'Connor Power, MP, on a non-political subject. The chair was taken by Mr. J. G. Biggar, MP. On rising to introduce the lecturer, he soon discerned that trouble was impending, that there was, so to say, "a storm in the offing." An "Advanced" person, a Mr. Flesh of Ramsbottom, came on the Platform and informed him that at a meeting of Nationalists held on the previous evening, it was decided that the lecture might be allowed to proceed only on the condition that the lecturer should first answer satisfactorily a series of questions which had been drawn up for him. The main purpose of those interrogatories was to ascertain whether he held and was prepared to support the principles of Wolfe Tone, Lord Edward Fitzgerald, and Robert Emmet. The chairman said those questions were not in order, as the lecture was to be on a non-political subject; however, he would leave it to the lecturer to deal with the queries as he thought fit, Mr. O'Connor Power then came to the front and said, amidst much noise, that with regard to the questions that had been read, his view was identical with that of the chairman. He begged leave to point out - He could say no more: the platform was rushed; there was a smashing of chairs and tables, a noise of heavy blows, and of fierce exclamations from men engaged in close combat, mingled with the shouts and screams of women, while blood flowed freely from many wounded persons ... The subject of Mr. O'Connor Power's intended lecture was "Irish Wit and Humour".
O'Connor Power delivered the lecture, within a fortnight, in the same hall, and Biggar again presided. This time, "the Irish of Manchester and Liverpool, revolutionaries and constitutionalists, banded together to put down any rowdyism should it again arise; but instead of that, O'Connor Power was received with 'deafening cheers, again and again repeated' according to a newspaper report".
O'Connor Power had an uneasy working relationship with Parnell, who he thought was "a mediocrity". T. M. Healy narrates an incident from 1878:
... I wrote Maurice:
"Would it be possible to get up a meeting in Lismore, and invite Parnell? The resolution I moved in Dublin at the Confederation of Great Britain was at his request, upon a suggestion of my own. If he could have O'Connor Power at his elbow continually it would be a good thing, as Power understands the necessities of agitation, and Parnell doesn't. I hope he will make a good fist of his answer to Butt, though I have never been persuaded that he shines as a letter-writer. Dan Crilly told me Parnell's first contribution to the Liverpool Argus (mentioned in my London letter) was not worth much, and though he promised to insert it, he has failed me."
O'Connor Power and Parnell were not kindred spirits. Power was an able and eloquent man, "reeking of the common clay", at which Parnell's aristocratic sensitiveness recoiled. "Of their differences I hinted to my brother":
24 November '78.
"I met O'Connor Power, and he was unaware, until I told him, that his name was down to propose one of the resolutions in Dublin. He expressed disgust, and said he told the Dublin people he would not go over, and that it was only another piece of their cowardice in being afraid to face Butt themselves.
I was aware of the stories told about Power, but what is the use of repeating them? Parnell has been careful to tell me his views about Power (and so has Biggar), but I have defended him to them, and think they should make allowance for his poverty and position. Parnell told Power to his face that he was "a damned scoundrel," and Power made a coarse reply ..."
After Parnell and Davitt addressed the follow-up meeting at Westport, County Mayo on June 8 1879 they took control of the growing Land War. T. M. Healy gives his view of how O'Connor Power was frozen out of the Land League:
Stirrings of ambition and resentment may have been ingredients in Parnell's action in joining Davitt and cold-shouldering Power, but what can lessen admiration for the pluck with which he threw himself into a movement which involved him and his relatives in danger and loss? His rents in Co. Wicklow and those of his brothers in Armagh and Carlow were at stake.
Towards the close of the session Power wrote me:
If you have seen my article in the Fortnightly, I would feel obliged by your noticing it in your letter this week. The cynical Saturday Review noticed it fairly enough, but I have seen no notice of it in any Irish paper."
J. O'Connor Power.
I complied, but owing to his strained relations with Parnell and Biggar, he went to Dublin to examine the position, and wrote me:
"... Davitt met me on my arrival here – a reception unexpected on my part. He is writing an appeal to the Irish at home and abroad, for funds to carry on the Land agitation, and working hard to abolish the Home Rule League.
I am here just in time for Thursday's meeting, when the Home Rule League will be "tried for life" and perhaps condemned. Parnell's resolutions evidently tend in that direction."
Power's letter was written from the lodgings of Tom Brennan, who three months later, became secretary to the Land League, when Davitt was made its chief organizer, and Parnell (with Dillon) was accredited envoy to the United States.
Power, who started the movement, was left "festering outside-the breastworks," without control or influence in the new organization.
Though originally a friend, Davitt changed his opinion of O'Connor Power, describing him in his 'Jottings In Solitary' of 1881-1882 as a "renegade to former nationalist principles: unscrupulously ambitious and untrustworthy". Davitt became close to O'Connor Power in later years. Michael MacDonagh wrote "O'Connor Power was above the suspicion of interested motives".
He expressed interest in the Irish language.
He stood as a Liberal in Kennington (a seat with a substantial Irish electorate) in the 1885 general election, losing to a Conservative candidate; and attempted as a Gladstone Liberal to regain in his old heartland, Mayo West in 1892, losing to a Anti-Parnellite Nationalist. He stood as a Liberal (Radical) candidate for Bristol South in the 1895 general election, but again failed to re-enter Parliament.
In the course of the Bristol South election, he threatened legal action when a Conservative paper accused him of having taken the oath of an illegal organisation.
He had been taken up in London by the philanthropist Lady Jersey, which provided him with escape from poverty and the opportunities, for which he was scorned by political colleagues, to mingle with London society. In 1893 he married the wealthy widow of a surgeon. He was married for over two decades and his wife was at his bedside when he died peacefully in his own home.