Large-scale electoral meltdowns are relatively rare. In Italy in 1994 the Christian Democrats went from having been the biggest party in every election since the late 1940s to virtual wipe-out. In Spain in 1982 the Union of the Democratic Centre, which had dominated the first parliament after the transition to democracy, fell from 168 seats to just 12, and effectively ceased to exist. The biggest single defeat for any party was probably that of the Progressive Conservatives in Canada in 1993, who fell from 151 seats to just two, though they later recovered.

By all accounts, Fianna Fáil, the ruling party in Ireland, is facing electoral meltdown on Friday. The party first came to power in 1932, and has governed with an overall majority or as the leading party in a coalition for nearly 60 of the last 80 years. Only twice in that time has their vote fallen below 40 per cent, and then by a hair’s breadth: 39.1 per cent in 1992 and 39.3 per cent in 1997. The party has never lost two elections on the trot, and in 2007, the last election before the collapse of the Celtic Tiger, they won 42 per cent, just 3 per cent less than they had won in 1932. This is an amazing record, but it’s about to end.

The latest polls suggest that Fine Gael, the long-term Laurel to Fianna Fáil’s Hardy, will be the biggest party and may even win an overall majority. This would also be a turn up for the books. The last time Fine Gael (or its predecessor, Cumann na nGaedheal) was the biggest party in the Dáil was following the 1927 election, and they have never recovered that position since being knocked aside by Fianna Fáil. In 1932, they won 35 per cent of the vote; in 2007, they won 27 per cent. Labour, meanwhile, the third party in the system, winning 8 per cent in 1932 and 10 per cent in 2007, now looks like gaining a lot, but not as much as had been hoped for at the beginning of the campaign. Three weeks ago there was much media speculation that Eamon Gilmore, the Labour leader, might become taoiseach. Now, with Fine Gael wining big, it is not even certain that Labour will be part of the coalition.

Most observers of Irish politics, as well as most rational Irish voters, have always puzzled over the real extent of the differences between Fianna Fáil and Fine Gael. They have their origins on opposite sides of the 1922 civil war, but these days both are centre-right parties with a populist touch and privileged access to the Catholic hierarchy, and it’s difficult to distinguish their policies. Their cultures are far apart, however – or used to be. Fine Gael has tended to be favoured by old money, Fianna Fáil by new. Fine Gael was traditionally supported by professionals – doctors, lawyers and anybody else who could put a brass plate outside their offices – while Fianna Fáil has been favoured by the property developers and the men in mohair suits. Fine Gael notables used to go to fee-paying schools, Fianna Fáilers to the Christian Brothers. Fine Gael supporters are more likely to drink Smithwick's; Fianna Fáilers, Guinness. Fine Gael was the party of Garret FitzGerald – or Garret the Good, as he was known. Fianna Fáil was the party of the late Charles Haughey, or Charlie the Corrupt. Fine Gael has gone into the present election with a pledge to scrap the requirement to take Irish as an exam in the school Leaving Certificate. Fianna Fáil, one of whose stated aims is to restore Irish as the vernacular, disagrees.

Fine Gael’s great strength has always been that it was not Fianna Fáil, and that it was better at not being Fianna Fáil than any other party. Now that Fianna Fáil, in coalition with the Greens, has led Ireland into economic disaster, this is a great advantage. If Fianna Fáil goes into electoral meltdown on Friday, however, and if it then disappears from the Irish political landscape, there will be nothing left against which Fine Gael can define itself. Unless, that is, it can take advantage of the newly created gap on the Irish electoral market and become Fianna Fáil.