According to O’Tuathaigh , he would become the political leader who would articulate Catholic grievances in the most effective way. In order to do this, O’Connell exercised brinkmanship to threaten the government that social unrest was imminent unless reforms were granted. This was used in the 1828 County Clare election where O'Connell won the seat with 2/3 of the vote. This posed a problem for the government as O'Connell would not have been able to take a seat in the commons without a change of law. Peel knew a Catholic Emancipation agreement must be worked out as violence was inevitable so a bill was forced through Parliament, thus creating a success for constitutional nationalism.
O'Connell's ability to find success in failure meant constitutional nationalism could succeed. This was seen by how the Municipal Corporations Act became an instrument for O’Connell; he used it as an effective argument in support of repeal and it helped to generate agitation to the Union among many Irish.
Simply the events at the time were what allowed constitutional nationalism to flourish. Poor harvests in 1842 led to economic distress throughout Ireland. Admittedly, it was, once again, O’Connell skill as a leader which meant he was able to exploit the situation in order to create a sense of injustice and supplement support for repeal. Lecky describes how he was able to reconcile Catholic Ireland to the idea that constitutional nationalism would solve Ireland's problems, this in turn allowed the movement to develop successfully.
Constitutional nationalism's success also depended on the support of the enfranchised 40 shilling freeholders. Through them, O’Connell was able to prove significant electoral support for emancipation and form an embryonic Irish party. Catholic voters had even defied their Protestant landlords to vote for O'Connell in the County Clare by-election which is evidence to Lecky's belief that O'Connell awakened their political conscience, made them believe they could initiate change and encouraged them to vote. Then when their support was lost, after O’Connell’s success during the emancipation campaign led to the disenfranchisement of the 40 shilling freeholders, his electoral following plummeted, forcing him to postpone his goals and compromise. Essentially, O'Connell's leadership was useless without any initial support.
The Church played a major part in the lives of Catholics, particularly the peasantry, and in turn, in the future of constitutional nationalism. At a local level, the Clergy helped both the emancipation and repeal campaign in the same way, collecting the Rent and becoming local leaders in the movement. They also expanded interest in the organisation within communities. The Catholic Church was the crucial link between cultural and constitutional nationalism which was essential for the success of the latter.
Political circumstances must also be remembered when reviewing what is responsible for the growth of constitutional nationalism. O’Connell faced the weak and divided government. Wellington’s administration was in no position to challenge O’Connell and was forced to concede defeat on catholic emancipation. Therefore the weakness of the British Government was a major contributor to the success of constitutional nationalism.
The Whig administration was governing with only a moderate majority, providing constitutional nationalism with a valuable opportunity. The movement was in a position to enjoy the balance of power in Westminster. Through a Whig-O'Connellite alliance, they managed to secure limited reforms for Ireland on issues of local government, law and order (such as the Constabulary Bill and Judiciary Bill), and poverty. These were of immediate importance to Ireland so while not Repeal, were an undoubted success for Irish nationalists.
After the disaster of the Clontarf meeting, O’Connell was jailed for sedition. Along with old age and deteriorating health, this affected O’Connell’s leadership and he became much less radical and more withdrawn. His death meant the movement found itself badly organised, divided and leaderless. The period between the Act of Union and 1820 saw a lack of Catholic political leadership so when he filled that void, he gave hope and constitutional nationalism thrived. The historian Lecky reinforces this idea by claiming that O'Connell did more than anyone else did for the development of Irish nationalism. The fact that the movement nosedived after his death is testimony to his importance.
In O’Connell, the movement found the leader it wanted, and the leader it had never had. His skill in oratory was, while creating rapport with the Catholic masses, to tacitly threaten the British Government with open rebellion. A dangerous but effective policy of brinksmanship won him support among urban and rural Catholics alike. Yet O'Connell's leadership skills would not have been enough without the support of the clergy. The political situation in Britain also had a big influence on the movement's development, when the government was strong it could limit reform; it had to resort to compromise when weaker. Nonetheless, it can be argued that they only achieved as much as the British government wanted them to achieve. So although the leadership of O'Connell was the main reason for constitutional nationalism's success in the mid 19th century, it wasn't the only one.