Sinn Féin has completed a historic hat-trick for Irish nationalism by becoming Northern Ireland’s biggest party in local government, the Stormont assembly and Westminster. On 4 July it increased its majorities in several constituencies and whittled those of opponents, teeing up potential gains in the next general election. Meanwhile, the party’s vice-president, Michelle O’Neill, has made history as the first nationalist first minister. Last month Leo Varadkar, the former taoiseach, said the next Irish government must prepare for a referendum on Irish unification. Last week Ivana Bacik, the leader of Ireland’s Labour party, wrote to Keir Starmer saying “work must begin to take place now” on a poll. It may seem the stars are aligning for a referendum, which under the Good Friday agreement a Northern Ireland secretary of state must call if a majority appears to favour unification. In fact, the prospect remains remote. Sinn Féin’s symbolic breakthroughs in Northern Ireland do not represent a surge in support for unification, which has stalled. The party’s ratings in the Irish republic have slumped, deflating its chances of leading the next Dublin government. The Scottish National party’s collapse has killed hope of Scotland starting the breakup of the UK. Starmer has ideological and political incentives to bury the referendum issue. “The new Labour government is unambiguously pro-union,” said Peter Shirlow, the director of the University of Liverpool’s Institute of Irish Studies. “We ended up with the most pro-union parliament since 2011.” The combined vote share for Sinn Féin and the moderate nationalists of the Social Democratic and Labour party (SDLP) has hovered around 40% since 1998, a stagnation that has persisted despite Catholics overtaking Protestants (45.7% v 43.48% in the 2021 census) and despite Brexit, which fuelled antipathy to London. The combined vote for parties who favour remaining in the UK hovers around 43%. Sinn Féin has overtaken the Democratic Unionist party as the biggest party not by winning converts to Irish unity but mainly by taking votes from the SDLP, while for its part the DUP has lost votes to the Ulster Unionists, Traditional Unionist Voice and independent unionists. This fracturing was a political crisis for unionism but not a referendum crisis, Shirlow said. “Most people are now middle income, have decent incomes, lower mortgages than their southern counterparts and other reasons why they remain pro-union.” Quality of life often trumped identity, he added. “Survey after survey shows more Catholics wish NI to remain in the UK than Protestants want a united Ireland.” Hilary Benn, the new secretary of state for Northern Ireland, has echoed his boss’s declaration last year that a referendum was “not on the horizon”. Benn has rebuffed calls to spell out the exact criteria for calling a referendum – potentially a mix of opinion polls, election results and demographics – which clouds the goalposts in a convenient mist. Some warn that this risks storing up trouble – that the conditions could be met within a few years and no one will be ready, paving a hasty, Brexit-style campaign with profound consequences. Approximately 15% of people vote for Alliance, which takes no position on unity, though most of its supporters have long been perceived as soft unionists. Gerry Carlile, the head of Ireland’s Future, which advocates a referendum, challenged that assumption. “If there is no majority for a united Ireland, and none for the union, where does that leave us? Does that not suggest we need to ask the people?” “We’re looking at 2030 as a tipping point of sorts,” said Carlile, citing social, demographic and political trends. “If you know something is coming, you get ready.” Brendan O’Leary, a politics professor at the University of Pennsylvania and the author of Making Sense of a United Ireland, said a region-wide election won by a majority of parties and independent candidates who openly call for a referendum was conceivable – and should be respected by the UK government. “If nationalists won a majority of seats in the assembly, or if nationalists and Alliance and other ‘others’ voted for a referendum to be held in the assembly, then I think the secretary of state should respect that resolution, provided they have a majority of the first-preference vote between them,” he said. O’Leary did not think there was a case for a referendum in the lifetime of this Labour government, or at least not now, but said the next Irish government should consider preparing a prospectus on reunification, developing a ministry of national reunification and holding a constitutional convention. On the British side, meanwhile, the calculus is clear: sit tight.