2015–2019: Foundation and early elections The Social Democrats was established with a co-leadership arrangement between its three founding members.
Róisín Shortall is a former
Labour Party TD and former
Minister of State at the Department of Health. She resigned from the role and from Labour in September 2012, citing lack of support and the lack of an explanation from then-
Minister for Health James Reilly concerning his controversial decision to locate a new
primary care centre in his own constituency.
Catherine Murphy was successively a member of the
Workers' Party,
Democratic Left and the Labour Party before being elected as an independent TD in 2005.
Stephen Donnelly first entered politics as an independent TD in the
2011 general election, having previously worked as a consultant for
McKinsey and Company. Both Murphy and Donnelly were members of the
Technical Group in the 31st Dáil, with Murphy having served as its
Chief Whip. The party ran fourteen candidates in the
2016 general election, including its three incumbent TDs, former Labour Party
Senator James Heffernan, and county councillors
Gary Gannon and
Cian O'Callaghan. Their three incumbent TDs were re-elected, but none of their other candidates were elected. In May 2016, the party formed a technical group within the Dáil with the
Green Party. On 5 September 2016, Stephen Donnelly resigned as joint leader and left the party, stating that he was doing so "with great sadness, having vested so much together with my parliamentary colleagues, Catherine and Roisin, a small core team and many volunteers across the country, into the establishment of the Social Democrats over the last 20 months", but referring to his relationship with his fellow leaders, that "some partnerships simply don't work". On 2 February 2017, he joined
Fianna Fáil.
2019 local and European elections The Social Democrats contested their first
European Parliament elections in May 2019, with councillor
Gary Gannon running for election in the
Dublin constituency. Gannon received 5.6% of the first-preference votes, finishing 6th out of 19 candidates in the first count. He was eliminated on the 14th count. The party did not contest the other Irish constituencies of
Midlands–North-West or
South at this election. The party also contested their first local elections in May 2019. The Social Democrats put forward 58 candidates for seats on local councils. 55% of the candidates were women, making it the second highest percentage of female candidates put forward among all political parties. 19 of the 58 candidates were elected, more than trebling the party's representation in local government.
Ellie Kisyombe, a
Malawi-born asylum seeker running for the Social Democrats in Dublin's North Inner City LEA, was retained after a review of inconsistencies in her account of her asylum history and time in
direct provision; following this, three members of the party's National Executive resigned.
2019 by-elections and the 2020 general election In November 2019, the party contested 3 of the 4 by-elections caused by the election of Irish TDs to the European Parliament, but did not win any seats, with their candidates all receiving between 2.5% and 4.4% of the vote. In the
2020 general election, the party ran 20 candidates in 20 constituencies, and increased their seats to six, despite a small fall in the number of first preference votes received. Murphy and Shortall were re-elected in their constituencies, and were joined by
Holly Cairns in
Cork South-West,
Gary Gannon in
Dublin Central,
Cian O'Callaghan in
Dublin Bay North and
Jennifer Whitmore in
Wicklow. The Social Democrats finished level on seats with the
Labour Party and exceeded the seats of other left-leaning parties
Solidarity–People Before Profit and
Independents 4 Change.
Holly Cairns as leader On 22 February 2023, Murphy and Shortall announced that they would step down as co-leaders of the Social Democrats. Holly Cairns was the only candidate to put her name forward for leadership of the party, and she was announced as the new leader on 1 March. On becoming leader, Cairns reiterated that the Social Democrats have no interest in merging with the Labour Party, which had been repeatedly suggested but rejected by the Social Democrats' party leadership. She said that housing and Sláintecare would be red line issues for the Social Democrats in any coalition talks with any party. On 4 July 2023 it was announced that Cian O'Callaghan had been appointed to the newly created role of deputy party leader.
2024 elections In the
June 2024 local elections, the Social Democrats ran 78 candidates, with 35 elected, including 10 on
Dublin City Council, where they became the second largest party. For the
2024 European elections in Ireland, the party ran three candidates, one in each of the Irish
constituencies. While the Social Democrats' first preference vote share increased to 2.95%, none of their candidates were elected. At the
2024 general election in November, the party almost doubled its number of TDs, going from 6 to 11, tying with Labour to become the fourth-largest party in Ireland. The party also gained its first Senator in
Patricia Stephenson at the
2025 Seanad election. However, the party lost a TD at the same time following the indefinite suspension of
Eoin Hayes. In July 2025 Hayes was readmitted to the parliamentary party. Shortly after Hayes' readmission, Galway city councillor Eibhlín Seoighthe resigned from the party.
2025 presidential election The party jointly nominated
Catherine Connolly in the
2025 Irish presidential election as part of a broad left-wing alliance. They first announced their intention to support Connolly on 11 July 2025, alongside
People Before Profit,
100% Redress and several
independent politicians.
Jennifer Whitmore said she was the overwhelming choice of party members. == Elected representatives ==