In March this year at a St Patrick’s Day parade, Mary Lou McDonald, leader of Sinn Féin in the Republic of Ireland, marched behind a banner that read “England get out of Ireland”. The stunt garnered widespread criticism. Taoiseach Leo Varadkar’s deputy, Simon Coveney, didn’t mince his words when he called it “offensive, divisive and an embarrassment”.

This incident was symptomatic of a party that has misread the room. Growing support for a united Ireland is clear: in late May, a poll conducted by RTÉ found that two-thirds of voters in the Republic supported a united Ireland, a marked contrast to a similar poll in 2015 that put the figure at just over one third.

But that support has departed from the type of nationalism Sinn Féin invokes. Boris Johnson’s current approach to Brexit – no backstop, or no deal – is obviously concerning for Northern Ireland’s economic health. Sinn Féin should be able to capitalise on this. And yet, the party is tanking in the Irish polls: the party suffered huge defeat in local elections across the Republic in May.

A new case for Irish unity has been ignited by Brexit, one grounded in economic logic, shorn of unpalatable historic reference, and championed by moderate Irish politicians. As Varadkar himself recently warned, “People who you might describe as moderate nationalists or moderate Catholics, who were more or less happy with the status quo, will look more towards a united Ireland… I think increasingly you’ll see liberal protestants, liberal unionists, starting to ask the question as to where they feel more at home.”

A few years ago no leading Irish politician would have touched this subject. Moderate politicians have long feared that broaching the subject would upset the sensitive peace in the North. In 2016, there was widespread shock when then-Taoiseach Enda Kenny spoke of the prospect of a united Ireland. Now, though, Varadkar, and his government, speak freely – if carefully – about the prospect.

But their case is entirely different to that of Sinn Féin. The argument is no longer tied to the Troubles, and an accompanying anti-English sentiment: it has been over 20 years since there was protracted violence in the North. Now, there is a whole generation that doesn’t associate nationalism with that violence.

Varadkar himself is nearly of this generation: the Troubles were over before his adult life, and the entirety of his political career has been spent in the European Ireland of the 21st century. So his case is about the political realities of Brexit, not an emotive response to historic injustice.

Rather than aping the language of Sinn Féin, the new nationalism of Fine Gael and Fianna`Fáil emerges from political and economic pragmatism. If Northern Ireland finds itself economically isolated by Brexit, those North of the border will have tangible reasons to look again at the prospect of Irish unity. The moderates' argument is only strengthened by reference to the failure to restore power sharing in Stormont.

The call for a united Ireland, then, is no longer the sole domain of Sinn Féin. It is still a distant reality – unionists still outnumber nationalists in the north. But, when that case is made by Varadkar and Coveney, moderates who don’t come from a republican tradition are more likely to listen. The prospect of a united Ireland is granted mainstream legitimacy.

As Fine Gael and Fianna Fáil reclaim the republican mantle from the fringes of Irish politics, parties across the UK concerned for the survival of the Union should be wary. The concern is no longer a banner reading “England get out of Ireland”. It’s that nationalism is finding a credible face.

Finn McRedmond is an Irish writer who covers politics for Reaction.