Sinn Fein the Workers' Party began to make an impact on the political scene at a time when Labour was demoralised and in some disarray.
In the late 1970s and early 1980s Labour was driven with divisions over whether it should go into coalition governments with Fine Gael and engage in the necessary major compromises on policy. SFWP arrived as a more clearly ideological left-wing party, opposed to coalition and committed to building its base among the disaffected in urban areas.
And build it did, directly in competition with Labour and often taking seats which Labour regarded as "traditional" seats of its. In fact, the pattern was that Labour had lost most of these seats without any competition from SFWP, and that party took the seats only at later elections. But that did not stop Labour complaining that SFWP was targeting its seats, rather than those of Fianna Fail and Fine Gael.
SFWP denounced Labour regularly for selling out through entering coalition. Labour figures responded by raising questions about SFWP's alleged links with the Official IRA in Northern Ireland.
Meanwhile, in the Republic, SFWP was threatening or capturing seats held or formerly held by Labour deputies. At its height it seemed poised to challenge Labour for pre-eminence on the left, taking the urban seats and leaving Labour as a rump of rural fiefdoms.
Its first Dail breakthrough came in the 1981 general election when Mr Joe Sherlock became its first TD, elected in Cork East. Very soon it had three deputies when in February 1982 Mr Proinsias de Rossa (Dublin North West) and Mr Paddy Gallagher (Waterford) joined Mr Sherlock in the Dail.
Labour, meanwhile, was convulsed by crisis. The pro-coalition policy favoured by the leader, Mr Michael O'Leary, and the majority of his parliamentary party was resisted by Mr Michael D. Higgins and a substantial section of the party's administrative council and membership. Labour won 15 seats.
In 1987 SFWP - now just The Workers' Party - won four seats, and in 1989 it reached its high point with seven Dail deputies - Mr De Rossa, Mr Sherlock, Mr Tomas Mac Giolla, Mr Pat McCartan, Mr Eric Byrne, Mr Eamon Gilmore and Mr Pat Rabbitte.
However, developments in Northern Ireland, in the former Soviet Union and within the Labour Party put an end to the party's growth. Continuing media reports about the Workers' Party alleged links to paramilitary activity in Northern Ireland, as well as the questioning of the nature of socialism after the break-up of the Soviet Union, contributed to the atmosphere that led ultimately to Democratic Left breaking away from the Workers' Party.
The reorganisation of the Labour Party and the healing of internal divisions under the leadership of Mr Dick Spring propelled Labour to its greatest election victory in 1992, when it won 32 seats. Democratic Left won four seats.
In 1994 the two parties ended up in government together and the unasked question became more and more obvious: why are there two separate parties on the left, in government together, with no major policy differences between them?
Discussions between the two parties on future policy co-operation began last autumn. In April DL began a lively internal debate on its future after two poor by-election results. In June talks began on the prospects for a new "formation" between the parties. This is the process which those least ambitious for it believe will end up in a formal alliance, and the most ambitious think will lead to a union of the parties before the year is out.