SF leader has made her party mainstream against the odds
There has never been a female Taoiseach - in a century, not a whisper of it. Just let that settle for a moment. We've had a number of women as tánaiste, but male leadership of the Irish State has appeared to be a permanent arrangement.
Now the lie of the land has upended. The Taoiseach automatically being a man looks like a rather more temporary idea. Mary Lou McDonald has achieved what no female party leader has done before in Ireland - she has muscled into the two-party boys' club and told them to budge up because they can't have it all their own way any longer.
Change can be a slow fuse or it can kindle and catch fire in a heartbeat. Here, we're looking at a sudden transformation of the political landscape. If Sinn Féin had run more candidates, Ms McDonald would be in the shake-up for Taoiseach. Even so, could she be one of two rotating Taoisigh? It's all to play for once negotiations begin.
Repeated attempts by Fianna Fáil and Fine Gael to exclude her have failed. She captured the public mood for change. The message from the election result is unmistakable. People are saying we belong to a community and not an economy. They can see homes aren't being built - and it's not because of land shortages or planning issues or money lacking, but because of ideology. After all, the skyline is dense with cranes. But office blocks and hotels are going up as opposed to social and affordable housing.
Why did Ms McDonald connect in a way the leaders of the two other big blocs struggled to do? Articulate and passionate, her communication skills are better - she spoke to people plainly about the issues that concern them. Brexit didn't figure.
Her party's policies reflected the public's needs, identifying housing, health, pension inequality and the crippling cost of living, such as crèche charges. The public showed itself less troubled by Sinn Féin's struggles to transition from its past, although in this area her surefootedness deserted the party leader during the election campaign.
By contrast, Fianna Fáil and Fine Gael wasted time and energy attacking Sinn Féin rather than saying what they'd do for people if they had the good fortune to be elected. That negativity backfired.
Regardless of how many seats Sinn Féin ends up with, she won the popular vote. Her party is a contender now against the two traditional parties which emerged from the Civil War and dominated Irish politics throughout the 20th century. Odd to think that Sinn Féin may have done more to end this protracted, irrelevant Civil War divide than any other.
A Fianna Fáil-Sinn Féin coalition, with some additional support from others, is the obvious solution to the government formation conundrum. That means constitutional change for the island of Ireland has just picked up pace because Sinn Féin is a 32-county party.
Coalition between these two parties is logical. Once they were indistinguishable. Remember, Fianna Fáil was a breakaway party from Sinn Féin - in 1926, De Valera and supporters including Countess Markievicz separated to form Fianna Fáil.
This Sinn Féin quake has been categorised as a youth vote but it's broader than that. Ms McDonald's progressive position on social issues, such as abortion reform, has drawn some new, middle-class and middle-aged voters towards her party.
She is a feminist and unapologetic about it. Last summer, I attended an event in Deansgrange Cemetery in Dublin to commemorate Dr Kathleen Lynn, the revolutionary and social activist who co-founded Ultan's Hospital. The Sinn Féin leader slipped in quietly on her own among the gathering - simply there to pay her respects. Later, she told me Dr Lynn was one of her heroes.
Among those choosing the party at the ballot box were other women weary of the male hegemony. Leo Varadkar hasn't been a trailblazer about promoting women and Micheál Martin has a shortage of them in his party ranks.
Why else did she stand out? Ms McDonald spoke with passion about her vision for Ireland, it was radical and notably different to that of Mr Varadkar and Mr Martin, whose narratives were interchangeable. Voters also noticed how she took no nonsense from male colleagues in the cut and thrust of politics. She is an able performer on television and radio, as well as in Leinster House. Any party would be glad to have her as a member.
It is hyper-simplistic to categorise this as an anti-Establishment or protest vote. People took the trouble to inform themselves on what was on offer and voted to shape the State's future direction.
The Sinn Féin brand has turned some little-known candidates into TDs. It has also convinced voters it's the go-to party of the left. Even if Sinn Féin doesn't make it into government, it will have an impact on the next administration because policies will have to tilt further left of centre than was intended by either Fianna Fáil or Fine Gael.
People want fairness. That's why persistent concerns crop up about the multinationals. Granted, they are massive employers, but there are well-documented instances of some big names paying less than the 12.5pc rate of corporation tax.
And we are weary of being told repeatedly that the State's fortunes have turned around post-crash when so many can't feel the benefits. Even for those who are managing, there is a sense of injustice - shame and outrage, too - at the housing crisis. We don't want to see small boys eat their dinner off a piece of cardboard while they sit on the pavement, or elderly women use an outer windowsill on Grafton Street as a table to rest their evening meal on, or homeless people taken to court for stealing a €1 bottle of orange or €3 worth of chocolate bars.
The traditional parties are being punished because of such cases. Here's a revealing snapshot from just one constituency: neither Micheál Martin nor Simon Coveney met the quota in Cork South Central and relied on transfers, whereas Sinn Féin's Donnchadh Ó Laoghaire topped the poll. Sinn Féin candidates are being elected in seats where the party has never had a presence.
A swathe of the electorate went out with intent to vote for change from the established order. It is not unexpected for young people to choose more radical options than their parents - but for the middle-aged to do so is unusual. Yet that's what happened.
Come what may, Sinn Féin has gone mainstream - persuading a significant cohort of voters that not only has it left its past behind but it can be an agent for change. Now its challenge is to persuade a divided and flummoxed Fianna Fáil party to enter into coalition. Sinn Féin has overcome much greater challenges than that.