The group once derided as the mouthpiece of the IRA attracted young voters by concentrating on social issues

People are in decent jobs making decent money, but the money is all going on rent,” says Kelly Doherty, a 24- year- old DJ from Dublin. “There is none left at the end of the day. Under the current government there doesn’t seem much sympathy for that.”

On Saturday, Ms Doherty joined almost a quarter of voters in the Irish Republic in giving her support to Sinn Féin, a party long treated as an outcast and reviled as the mouthpiece of the IRA during the latter’s violent 30-year campaign to force Britain out of Northern Ireland. She says she is “aware” of Sinn Féin’s relationship with the paramilitary group but believes Ireland has to move on and address today’s problems.

“It is an important step in the maturity of our country, that we recognise the past has happened and we move forward,” she adds.

For Sinn Féin it is a seismic breakthrough, one driven by deep discontent about quality of life — particularly among young voters with fewer memories of the Troubles in Northern Ireland that claimed more than 3,600 lives. The poll result has shaken the Irish political landscape and left its traditional ruling parties reeling.

The strongly nationalist, leftwing party gained 14 seats to finish with a tally of 37. It was just one seat shy of the centrist Fianna Fáil, which was expecting to return to government after losing power in 2011 in the wake of the country’s financial crisis. The result was especially disastrous for Leo Varadkar, the taoiseach or prime minister, and his centre-right Fine Gael, which trailed in third place after nine years in office.

Sinn Féin’s roots go back 115 years to Ireland’s struggle for independence from Britain, but it spent much of its life challenging the legitimacy of the Irish state established in 1922 and it still opposes the partition of six counties to create Northern Ireland. The party, which shares power in the recently restored devolved administration in Northern Ireland, now stands on the cusp of government in the south, though the other main parties say they will not join it in a coalition.

For some, last weekend’s election marks the latest chapter in Ireland’s transformation into a conventional left-right European democracy, with voters giving a mandate to a historically antisystem party. And in the process, the results have ended the duopoly of the two centrist parties which have been divided less by policy than enmity rooted in the civil war.

Brigid Laffan, an Irish scholar at the European University Institute, says: “If you look at the history of the Irish state and the party system born from the [1922-23] civil war, the first big wave of normalisation happened with Fianna Fáil [a split from Sinn Féin that first won an election in 1932, remaining the biggest party until 2011]. I regard this as a second big wave. I see this as closure of a process and a sign that Irish democracy is pretty robust.”

Others still recoil at the thought of Sinn Féin in power. “They are an authoritarian force,” says the Irish writer John Banville, who, at 74, has vivid memories of the Troubles. “They are not a political party as we know them in democratic societies.”

Sinn Féin had not anticipated its success. It only fielded 42 candidates in the race for the 160-seat Dáil assembly. But Mary Lou Mcdonald, the party’s leader since 2018, now has the upper hand in talks to form a government, a process that could take months.

Her preference would be to enter power via a leftwing coalition with the Greens, centre-left, hard- left and independents. But policy differences in such a disparate alliance may prove insurmountable. That would lead her back to Fianna Fáil. Like Fine Gael, it still harbours deep reservations about Sinn Féin’s IRA links and leftist, antiausterity policies that would add €22bn to public spending over the next five years while taking more tax from business and the wealthy.

Sinn Féin’s surge owes a lot to Ms Mcdonald, 50, who replaced Gerry Adams, the party’s president since 1983. Mr Adams was the public face of IRA violence during the Troubles and was also a prime mover in the strategy that led to the 1998 Good Friday Agreement that ended the conflict, and the decommissioning of paramilitary weapons in 2005. But his association with the violence — he denies ever being an IRA member — hampered the party’s progress in the republic long after it became the largest nationalist party north of the border.

A middle class, privately educated Dubliner, Ms Mcdonald first joined Fianna Fáil before switching to Sinn Féin. It was Mr Adams who marked her out as a rising star, says Christy Burke, a former IRA prisoner who was a Sinn Féin councillor for 25 years in Dublin and is now an independent. “Gerry came to me and said: ‘Take her under your wing. She has potential.’”

Mr Burke says he introduced Ms Mcdonald to the Dublin city centre constituency that is now her base. She was first elected to parliament in 2011 and quickly established herself as a sharp orator who could skewer adversaries. Her personal charm and connection with voters shone through on the campaign trail — in contrast to Mr Varadkar — although critics dislike her hectoring rhetoric.

Ms Mcdonald’s early leadership was marked by setbacks. Sinn Féin sank to a dismal 6 per cent in the 2018 presidential election, dropped seats last year in the European Parliament polls and lost nearly half its councillors in local elections. The party switched approach, relying less on negative attacks and more on its own policy proposals.

The policy ideas fell on fertile ground in a country that had gone through a decade of severe austerity after the eurozone crisis triggered huge bank bailouts, mass unemployment and emigration. Despite rapid economic growth under Mr Varadkar and near- full employment, there is widespread public anger at the lack of affordable housing and childcare, plus failings in the health service.

According to an exit poll published on Saturday, some 63 per cent of voters said they did not feel they had benefited from an improvement in the economy.

The housing shortage is a particular concern, especially among the under-35s. A recent study by the Central Bank of Ireland showed that only one new dwelling was built for every seven additional people in the population between 2011 and 2019. Rents have increased by 40 per cent in the past five years, while average earnings have grown by just 14 per cent.

Sinn Féin is promising a big increase in public housing, a rent freeze and interventions in the banking system to cap mortgage rates, policies that have sent bank and property stocks down since the election amid anxiety about a leftward turn in Irish economic policy.

“Sinn Féin has had a very important election for themselves, the party, but it’s off the back of very populist policies that they put to the people,” says Eoghan Murphy, the outgoing housing minister in Mr Varadkar’s cabinet. “Now they need to see if they actually make that a reality in government. I think they’ll find that very challenging.”

The party’s promises proved especially attractive to younger voters. Sinn Féin won the support of a third of under-35s but only 12 per cent of over-65s, according to the exit poll, a sharp generational divide that reflects two decades of peace.

In the working-class Ringsend district in Dublin, near where Google and Facebook have big offices, a desire for a fresh approach to Ireland’s social problems appears to have outweighed any residual concerns over IRA violence.

“I can look beyond that,” says Aisling Waters, a childcare worker who has voted for the party for a decade. “It would have been fairly Fianna Fáil-fine Gael around here. It’s slowly dwindling . . . I think they’ve had their chance.”

Tony “Deke” Mcdonald, a Sinn Féin activist in Ringsend, who is no relation to the leader, says it was clear on the doorsteps that there was momentum behind the party. “I could feel there was a big mood towards doing something different,” he says.

Tommy Murphy, a retired engineer who voted for Sinn Féin for the first time on Saturday after a lifetime of Fianna Fáil support, is impressed by the new leader. “I like Mary Lou, I wasn’t too fond of Gerry Adams,” he says, complaining that taxpayers are still saddled with the costs of the financial crash. “We’re still paying for it, still paying for the banks. You’ve got to give the worker a chance. People are just sick of paying every week through the nose.”

Mr Burke, the former Sinn Féin councillor, says paramilitary chiefs once had little interest in Dublin politics. Leaving prison in the 1970s, he was discouraged from becoming involved in the city’s politics or anti-drugs activism. “I remember the IRA leadership saying: ‘Listen, keep away from all that, there’s a war on.’”

Sinn Féin’s transformation into the most formidable electoral force in the republic started with Mr Adams’ pursuit of a dual paramilitary-political approach at the height of the Troubles in the 1980s — the strategy of