Irish politics

We believe that IRV leads to 2-party domination. Is Ireland evidence for that? Well, since 1921, Ireland's Dail has been elected by means of 3-to-5-winner multiwinner reweighted STV PR elections, not IRV. So Ireland cannot really be used to study IRV per se, and we would expect it to be a multiparty country.

However, Ireland's president really is elected by IRV (the single-winner special case of STV). That does not matter terribly much because the Irish president is a largely ceremonial position whose only real power worth mentioning is her ability to refer a bill to the supreme court for the purpose of testing its constitutionality. (The most powerful person is the PM.)

Anyhow, for whatever it is worth, so far every Irish president has been from one of two parties. In fact they have all been from just one party (Fianna Fail) except for Mary Robinson. The fact that she was able to win without the support of Fianna Fail for the only time in Irish history, was a single-time aberration perhaps related to her worldwide fame (e.g. she won the Nobel Peace Prize), the fact the FF candidate was linked to scandals, and the unusual absence of a credible contender from the Fine Gael party. (Analysis)

Years President Party
1938 – 1945 Douglas Hyde (all)
1945 – 1959 Sean Thomas O'Kelly FF
1959 – 1973 Eamon de Valera FF
1973 – 1974 Erskin Childers FF
1974 – 1976 Cearbhall O'Dalaigh FF
1976 – 1990 Patrick Hillery FF
1990 – 1997 Mary Robinson Labour
1997 – Mary McAleese FF

As a country with proportional representation based on reweighted STV, one would expect Ireland to be a multiparty country. However, perhaps because Ireland also features IRV (single winner special case of STV) elections, that causes it to be more 2-party dominated.

Political parties and seat counts in Irish Dial after 2002 elections (ENPP=3.5)
%Seats Party
41.5 Fianna Fail
22.5 Fine Gael
10.8 Labour
6.5 Sinn Fein
4.0 Progressive Democrats
3.8 Green Party
<0.8% each Socialists and others
Since the constitution was written in 1937, the prime minister has always been a member of either Fianna Fail or Fine Gael:

Years Prime Minister Party
1932 – 1948 Eamon de Valera FF
1948 – 1951 John Costello FG
1951 – 1954 Eamon de Valera FF
1954 – 1957 John Costello FG
1957 – 1959 Eamon de Valera FF
1959 – 1966 Sean Lemass FF
1966 – 1973 Jack Lynch FF
1973 – 1977 Liam Cosgrave FG
1977 – 1979 Jack Lynch FF
1979 – 1981 Charles Haughey FF
1981 – 1982 Garret FitzGerald FG
1982 Charles Haughey FF
1982 – 1987 Garret FitzGerald FG
1992 – 1994 Albert Reynolds FF
1994 – 1997 John Bruton FG
1997 – Bertie Ahern FF