Humphreys took her one-year-old granddaughter, Charlotte, to the polling station at Killeevan Central National School in Newbliss, Co Monaghan
The role of the Irish president, or Uachtaran na hEireann, is predominantly ceremonial, but the office holder is Ireland's head of state and is responsible for defending the constitution. Each term of office is seven years and a president can serve two terms, although Connolly has indicated that she intends to serve only one term if elected.
The competition between the women was dominated by fierce attacks from the Fine Gael camp, with the party accusing Connolly of "hypocrisy" over her work as a barrister because it included representing financial institutions that were enacting home repossession orders, even though she has spoken against such actions as a politician.
Connolly, a Galway West TD, has said she did "all kinds of work" but did not go into detail about the cases she was involved in. Both the Bar Council of Ireland and Jim O'Callaghan, the minister for justice, pointed out that under the "cab rank" rule, barristers are obliged to represent clients as they come to them in a fair manner.
A Fine Gael attack advert against Connolly caused a backlash within the party, with some supporters privately saying they were put off by the tactics.
Another issue for Connolly was her decision to employ an individual, Ursula Ní Shionnáin, for six months in 2018 who had been convicted by the Special Criminal Court in 2014 on firearms charges. The woman was a member of Eirigi, a socialist republican party.
Connolly also defended a 2018 trip to Syria with other Irish parliamentarians after pictures emerged showing her in the presence of a militia leader linked to war crimes. But she described it as "a fact-finding mission" and insisted she had no control over who approached her group.
Michael D Higgins, the outgoing president, was first elected in October 2011. He was then re-elected in late 2018.
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To be eligible to run in the election, you must be an Irish citizen aged 35 years or older. During the presidential race, a main point of discussion which emerged was how restrictive the route is for those who want to qualify to become a candidate.
In order to qualify, a candidate must be nominated by either 20 members of the Oireachtas -- where there are 174 TDs and 60 senators -- or at least four local authorities.
There are 31 local authorities in Ireland, but because a large number of parties of the left coalesced around Connolly, and the centrist government parties coalesced around Humphreys and Gavin, independent candidates found it impossible to secure the backing of the councils.
Those who attempted to get on to the ticket, but failed, included Bob Geldof, the Boomtown Rats frontman; conservative candidate Maria Steen; businessman Gareth Sheridan and controversial MMA fighter Conor McGregor.
The fallout from the 2025 Irish presidential election has already been particularly brutal for Fianna Fail. Micheál Martin, the party leader, backed Gavin, a former Dublin GAA football manager, despite some party members favouring an internal candidate, veteran MEP Billy Kelleher.
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It emerged during the campaign that Gavin owed a former tenant €3,300 in rent that was accidentally overpaid 16 years ago. Gavin withdrew from the race and Fianna Fail held a five-and-a-half-hour meeting where Martin was taken to task in what represented the biggest challenge to his leadership in years. The party has commissioned a review into what happened.
For Fine Gael, the fallout has already begun behind the scenes as party sources question the adversarial nature of Humphreys's campaign, and the PR associated with it, which some internally believed to be cringe-inducing. Humphreys was not the original candidate. That was Mairead McGuinness, former European commissioner, who dropped out in August on medical advice.
The big winners in the 2025 presidential election will likely be the parties of the left, including the Social Democrats, Sinn Fein, Labour, the Green Party and People Before Profit. They united around Connolly, offering her a significant campaign boost in terms of canvassing infrastructure and financial and staffing support.
Mary Lou McDonald, the Sinn Fein leader, and other parties will now argue that their backing of Connolly is evidence that parties of the left could feasibly form a government in future, but question marks remain over the stability of any such formation. The coalition government's term is scheduled to run until 2029.
The number of valid first-preference votes for each candidate is notified to the returning officer, who then calculates the quota. Because there is just one seat to be won, the quota will be 50 per cent of the total valid poll, plus one vote. With Gavin's name on the ballot paper, as he withdrew after the close of nominations, a vote for him is a valid vote and will be counted.
The new president will be inaugurated at a ceremony in Dublin Castle. The president lives in Aras an Uachtarain in the Phoenix Park, Dublin. The residence was built in 1751 and has been used as the official residence since 1938.