As a result of these murders, TF O'Higgins (Tom's father) was radicalised and would become a member of the Blueshirts, a radical right-wing paramilitary explicitly opposed to the IRA which eventually merged into Fine Gael, the political successor of Cumann na nGaedheal.

O'Higgins's political career began during the 1943 Irish general election when he unsuccessfully stood on behalf of Fine Gael in the Dublin City South constituency.

[2] In 1950, O'Higgins was one of eight members of the Oireachtas chosen to represent Ireland on the Council of Europe; it was the start of a lifetime interest in European politics.

He inherited a department mired by the aftermath of the failed Mother and Child Scheme and was now tasked with implementing the 1953 Health Act, which had been introduced by Fianna Fáil.

Doing so required O'Higgins to carefully manage both the Irish Medical Association and Fine Gael's coalition partners the Labour Party.

[2] In 1956, O'Higgins began to advocate internally in Fine Gael that the party needed to move away from the fiscal conservatism of the minister for finance, Gerard Sweetman, and managed to secure significant initial support.

[2] The culmination of this was Costello producing a document entitled Towards a Just Society which advocated that Fine Gael adopt social democratic policies.

[2] When Liam Cosgrave succeeded James Dillon as leader of Fine Gael in April 1965, O'Higgins was promoted to party spokesman on finance and economic affairs, replacing the conservative Sweetman.

The incumbent, an ageing Éamon de Valera, himself a veteran of the Easter Rising, was initially widely expected to either win easily or, more probably, stand unopposed.

O'Higgins, however, was not content with this and attempted to rally Fine Gael to support the Irish republican Seán MacBride in a presidential bid.

[2] Having campaigned so hard on the idea that someone must challenge de Valera, eventually party members turned the question back on O'Higgins and suggested he run.

Fine Gael leader Liam Cosgrove responded by arguing that this was unjust, as although de Valera was not formally campaigning, he regularly appeared on RTÉ radio and television in his capacity as president.

Sweetman described the O'Higgins campaign as expressing "the need for a youthful, forward looking president to personify the real Ireland and what it can best contribute to modern civilisation".

[6] Polling was not yet a feature of Irish politics in 1966; instead parties still generally relied on their constituency branches to provide a sense of grassroots sentiment.

Responding to the momentum of the O'Higgins campaign, Haughey announced £5.5 million in spending targeted at farmers just five days before voting began.

As deputy leader, O'Higgins made several trips to Northern Ireland in the face of the emerging Troubles and was one of the Fine Gael representatives at the funerals of those killed on Bloody Sunday in 1972.

In the aftermath of the general election, his diplomatic skills were once again called upon, as he looked to as a broker between Fine Gael and the Labour Party as they attempted to form a governing coalition, which was ultimately successful.

After the sudden death of Erskine H. Childers, O'Higgins, in his role as Chief Justice swore in Cearbhall Ó Dálaigh as President of Ireland.