Dáil & Seanad By-Elections
An Overview of all By-Elections to Dáil Éireann and Seanad Éireann since 1923
Dáil & Seanad By-Elections
An Overview of all By-Elections to Dáil Éireann and Seanad Éireann since 1923
After the election of Catherine Connolly TD to be the 10th President of Ireland, there must now be a By-Election in the constituency of Galway West to fill this vacancy. Incumbent President Michael D. Higgins will leave office after 14 years at on November 10th, with his successor being sworn in the following day, November 11th. Under the section 39 of the Electoral Act 1992 (as amended), a by-election to fill the vacant seat must occur within 6 months, so on or before May 10th, 2026. While parties prepare their candidates, it is worth reflecting on all By-Elections for both Dáil Éireann and Seanad Éireann seats vacated since 1923. As always, if you spot any discrepancies or have any questions, feel free to reach out to me at jamiepmce@gmail.com, or send me a message on any social media platform where we may be mutuals!
(due to the size of some of the graphs, maps, and charts, this page is best viewed on a desktop or laptop screen)
By-Elections to Dáil Éireann
There have been 138 By-Elections to fill vacancies of Dáil Éireann since 1923 (the 4th Dáil). The 4th Dáil saw the most by-elections in a single term (21), mostly due to a group of TDs from Cumann na nGaedheal resigning in protest at the Government’s handling of the 1924 army mutiny and its stance on Northern Ireland. 7 Dálaí have seen no by-elections, with that number due to fall to 6 upon the immanent 2025/26 Galway West By-Election, provided that the Dáil does not dissolve in the interim, of course.
Out of the 138 Dáil Éireann By-Elections since 1923, a majority have been won by Fianna Fáil (51), followed by Fine Gael (29).
The outcome of by-elections shows no meaningful incumbency advantage: the party holding the seat prior to vacancy retained it in 51.45% of cases (71 times), essentially the same as the proportion in which the seat changed hands. In other words, by-elections do not systematically favour continuity over change. Results are therefore almost evenly split between retention and loss, indicating that the previous party’s hold on the seat provides only a marginal predictor of the eventual outcome. While we can get an understanding of incumbent performance through the last dataset, a further analysis of the figures allows us a deeper insight into the success of both the government and opposition at the time of a by-election.
In the following classification system, by-election outcomes are grouped according to both the previous holder of the seat and the party that wins it. Government Gain and Government Hold indicate cases where the incumbent government either takes a seat from the opposition or successfully defends one it already held. Opposition Gain and Opposition Hold indicate cases where the opposition either wins a government seat or retains one it previously held. This framework allows each by-election to be evaluated in terms of its impact on the parliamentary position of the government and opposition without making normative judgments.
The by-election data show a roughly balanced distribution between outcomes favoring the government and those favoring the opposition. The government successfully retained or gained seats in 46.38% of by-elections, while the opposition held or captured seats in 53.62%. Individually, the most common outcome was Opposition Hold (34.78%), followed by Government Hold (26.81%), suggesting that incumbents, and particularly opposition incumbents, tend to retain their seats more often than they are lost. Overall, while the government performs moderately well, by-elections slightly favour the opposition, reflecting their potential as a mechanism for signalling voter dissatisfaction or shifting parliamentary balance mid-term.
The outcome of by-elections shows no meaningful incumbency advantage: the party holding the seat prior to vacancy retained it in 51.45% of cases (71 times), essentially the same as the proportion in which the seat changed hands. In other words, by-elections do not systematically favour continuity over change. Results are therefore almost evenly split between retention and loss, indicating that the previous party’s hold on the seat provides only a marginal predictor of the eventual outcome. While we can get an understanding of incumbent performance through the last dataset, a further analysis of the figures allows us a deeper insight into the success of both the government and opposition at the time of a by-election.
Turning to the causes of by-elections, this dataset shows that the overwhelming majority of by-elections were triggered by the death of a sitting TD, which accounts for 67.4% of cases. This indicates that natural attrition has historically been the dominant cause of mid-term vacancies in Dáil Éireann. Resignations are the next most frequent single cause, with 18.12% instances, reflecting voluntary departures for political, personal, or strategic reasons. Other causes are comparatively rare but demonstrate the diverse procedural and institutional factors that can trigger a vacancy. Disqualifications account for only 3 cases, showing that legal or eligibility issues are an infrequent cause of by-elections. Multiple-office rules also contributed a small number of vacancies, captured under the category “Incompatible office”, which totals 14 cases and includes appointments or elections that make a TD’s Dáil seat incompatible with a new role.
By-Elections to Seanad Éireann
Coming soon...