There was no question of Mr Lynch's position being undermined by his Government's 1973 electoral defeat. During his position of opposition, Mr Lynch surmounted two minor internal crises in Fianna Fail without difficulty.
The first was over the Littlejohn brothers affair, when he had to admit publicly, that he had forgotten an intelligence briefing informing him that the British spies and bank robbers had been in contact with a British junior minister.
The second was Fianna Fail's heavy defeat in the 1975 Mayo by-election.
On both occasions there was a massive groundswell of support within the party and from the general public.
The three most important decisions Mr Lynch took as Fianna Fβil leader during this period in opposition were the appointment of Seamus Brennan as general secretary of the party in 1973, the reappointment of Mr Haughey to the front bench in 1975 and the commissioning of Martin O'Donoghue to draft a new economic programme to combat recession.
political organisation there, transformed the Fianna Fail party machine into a modern vote-getting machine. This machine clearly shoed its superiority to Fine Gael and Labour in the 1977 election.
Mr Haughey had been the most loyal of the 1970 hawks since his dismissal, and it was a demonstration of Mr Lynch's ability to put personal differences behind him when he made Mr Haughey the spokesman on health and social welfare.
Mr Haughey played a major role in transforming the previously lacklustre performance of the Fianna Fβil front bench into that of an effective opposition. In the process, of course, the post-Lynch leadership of Fianna Fβil was put on the agenda.
Dr O'Donoghue had acted as an economic adviser to Mr Lynch as far back as 1970, but it was his reflationary policy of "priming the pump" to combat unemployment by large-scale public spending, as outlined in the Fianna Fβil 1977 election programme, which played a major role in ensuring the party's return to office and then created many of its future problems.
While in opposition Mr Lynch was awarded the Schumann gold medal in 1973 for services to European unity, notably for his decisive victory in the EEC referendum that brought the Republic into the European Community.
On the domestic political front, he played a crucial role in securing Fianna Fβil support for the Sunningdale Agreement and the short-lived power-sharing executive in Northern Ireland in 1974.
He was able to assure Fianna Fβil militants that the government did not intend to scrap Articles Two and Three from the Constitution and managed to hold the party to a bipartisan line on the north throughout his period in opposition.
In March 1974, he addressed the Cambridge Union and made perhaps his most comprehensive statement on Northern Ireland. In it, he said the vast majority of the people of Ireland eschewed force as a solution to partition and were committed to peaceful reconciliation.
"Reconciliation involves the acknowledgment by all traditions in our country of each other's basic aspiration," said Mr Lynch. "Those of us who aspire to the peaceful reunification of Ireland acknowledge the aspiration of the minority who seek to maintain the link with Britain.
"But with their intransigent insistence that we should recognise that as an aspiration as a de jure right fails to take account of the deep-rooted feelings and basic aspirations of the great majority of the Irish people, North and South, and this can perpetuate the historic agony of Ireland."
His speech was a defence of moderate constitutional nationalism and gradual social reform through parliamentary means. When the Sunningdale Agreement began to run into difficulties, initially over the recommendations of the Anglo-Irish Law Commission on extra-territoriality for the legal systems of Britain and Ireland, Mr Lynch opposed the proposals but made it clear that he still approved the overall agreement.
His principal criticisms were over the delay and piecemeal implementation of Sunningdale. After the power-sharing executive fell in May 1974, Mr Lynch went on record saying that he still supported the power-sharing concept although there appeared no immediate alternative to direct rule.
Nevertheless, Fianna Fail's position on the North gradually began to harden and Mr Lynch warned that a political vacuum in the North would encourage extremism.
In July 1975, he told the Dail that bipartisanship was in jeopardy because of statements by the Minister of Posts and Telegraphs, Dr Conor Cruise O Brien, that the government should not be actively seeking unity.
Mr Lynch also had several meetings with senior Britihs politicians on the North.
His relations with the two Labour Prime Ministers, Harold Wilson and Jim Callaghan, were particularly good. Mr Callaghan frequently holidayed in west Cork and paid social visits to the Fianna Fail leader.