O'Connell gained a significant following by 1830, he had over 30 Catholic O'Connellite MP's who formed a significant minority in the house of Commons. By 1847 O'Connell had died losing most of his support and influence.
Isaac Butt entered parliament as a liberal conservative in 1852. During his time as a Nationalist Leader he achieved winning 59 seats and outlined a reform of the Government of Ireland which would in turn end up dominating politics for decades. He gained much popularity among the Irish masses by defending the Fenians after the revolt of 1867 and led the Amnesty Association which campaigned for their release, he also founded the Tenant League, to renew the demand for Tenant rights. Butt also formed the Home Rule Association in 1870 and in 73 he turned the movement into a fully fledged political party - Home Rule Party. However, Butt was not very successful in his leadership as a small fraction became frustrated with him in 1875 and began to act on their own, which showed Butt's weakness as a leader. Another failure on Butt's behalf was that he had little control over the radicals who openly defied him and left behind a very divided party. Isaac Butt also had little impact on the House of Commons. Parnell took over the Home Rule association and ended up leading in with much better leadership than Butt could ever hope for.
John Redmond was an Irish Nationalist Politician, he became a barrister and eventually took over for Parnell in 1891. He played a pivotal part in Irelands history. At that time the Party recognised that the biggest obstacles to Home Rule came from the House of Lords, the Conservative party and the Unionist Party itself. The second Home Rule Bill had been passed in the Commons in 1893 but rejected by the Lords. However, the rejection of Lloyd George's "People's Budget" by the Lords in 1910 was to be of great significance to the Home Rule Party. A General Election was called which resulted in a victory for the liberals but they were dependent upon the support of Redmond and his party. Then came the Parliament Act of 1911 which meant that the Lords could delay the passage of Home Rule but could not veto it. The Third Home Rule Bill was introduced in April 1912 and this was to mark the high point in the political career of Redmond. Home Rule was now only a matter of time. However, Unionists in Ireland mounted strong opposition to the Bill. In September 1912 the Ulster Covenant was signed by 471,414 men and women who pledged to use "all means that may be necessary to defeat the present conspiracy to set up a Home Rule parliament in Ireland". In 1913 the Ulster Volunteer Army was set up to defy the government by force of arms if necessary. In 1914 the UVF successfully brought in a large consignment of guns and ammunition from Germany. 1913 also witnessed the formation of yet another private army in Ireland, namely the Irish Volunteers. They were under the leadership of the Nationalist, Eoin MacNeill and were totally committed to the cause of securing Home Rule for Ireland.
As 1914 began, Ireland seemed to be moving closer and closer to a civil war between the Ulster Volunteers and the Irish Volunteers. By the summer of that year the Third Home Rule bill was indeed on the Statute Book but with the outbreak of war, it's operation was suspended until after the war. In August 1914, thousands of Ulster Volunteers flocked to join the British army in order to demonstrate their complete loyalty to Britain and in this way succeed in having Home Rule abandoned completely. In order to ensure that Home Rule would be granted, John Redmond believed that members of the Irish Volunteers should also join the British army and in a speech in Co. Wicklow in September 1914 he pledged his support for the Allied cause and urged the Irish Volunteers to "account yourselves as men not only in Ireland but wherever the firing line extends in defence of right, of freedom and religion in this war." The majority of Volunteers heeded the call and by October 1915 there were over 100,000 Irishmen fighting on the side of Britain in the Great War. However, John Redmond was unhappy with the British War Office in their refusal to recognise his ideas of separate and distinct Irish regiments and the distinguishing insignia its members should wear. In Ireland a small group of nationalists saw the involvement of Britain in war as an opportunity to start a rebellion. This rebellion took place at Easter in 1916 when key buildings all around the city of Dublin were taken over by Patrick Pearse and his followers. However they were surrounded by British troops and within a few days were forced to surrender. The immediate reaction of most of the Irish public was one of disapproval as over 300 civilians died and millions of pounds worth of damage had been caused. Martial law was declared and the British authorities decided to execute the fifteen leaders of the rebellion. These executions had a dramatic effect on public opinion and aroused great sympathy and support for the rebel cause.
In the two years after the Easter Rebellion, nationalists began to support the Sinn Fein Party which supported complete independence from Britain instead of the Home Rule Party of John Redmond. In the General Election of 1918 the once powerful Home Rule Party was swept aside and the Sinn Fein candidates won an overwhelming victory. In the election the Home Rule Party was reduced to a mere six seats under the new leadership of John Dillon as Redmond had died in early 1918.
Eamon De Valera was a leader in the 1916 Easter Rising which proclaimed an Irish republic. He was arrested then saved from the death sentence because of his American birth and instead received a prison term. On his release, he stood as a Sinn Fein Party candidate in the 1918 general election. Sinn Fein won the majority of seats outside Ulster, but refused to take their seats at Westminster, instead establishing an independent parliament (Dail Eireann) to govern Ireland. De Valera was elected president of the Dail.
The Irish Republican Army, the armed wing of Sinn Fein, began a guerrilla war against Crown forces. After two years of violence, a truce was agreed and a treaty with the British negotiated by a Sinn Fein deputation, which de Valera chose not to join. Michael Collins, who led the Sinn Fein negotiating party, described the result as 'the freedom to achieve freedom'. But de Valera opposed the agreement, because it involved the partition of Ireland and did not create an independent republic. The treaty was passed by a narrow margin in the Dail and de Valera resigned as president. He led the anti-treaty side in a bitter civil war against the government of the new Free State. Despite killing Collins, the irregulars were defeated. De Valera opposed the treaty that established the Irish Free State, but went on to lead and shape the new state.
Looking over each of the Constitutional Nationalist Leaders it is a fair assumption that Parnell was not the most effective leader, yes he set the structure for the Home Rule Bill, which in theory set into motion the work of Redmond and De Valera, however, Redmond was effective in securing British support, whereas De Valera managed to rally the Irish people as well as gaining a treaty from the British, through the use of Collins, which freed Southern Ireland from British rule.