(Bloomberg) -- Northern Ireland’s government and assembly sat for the first time in two years on Saturday, with an Irish nationalist from the Sinn Fein party appointed as first minister, a milestone moment in the region’s turbulent history.

Michelle O’Neill, whose party campaigns to reunite Northern Ireland with the Republic over a century after partition, has been waiting to take on the role since May 2022, when Sinn Fein won the most seats in assembly elections.

Today “opens the door to the future,” O’Neill said in her first speech as first minister. “We mark a moment of equality and progress. A new opportunity to work and grow together.”

US President Joe Biden said he welcomes and strongly supports the restoration. “This is an important step,” he said in a statement.

O’Neill, 47, had been prevented from taking up her role by the Democratic Unionist Party, which quit the power-sharing institutions to protest Brexit trading rules it said were weakening Northern Ireland’s position within the UK.

The DUP this week reached a deal with the British government to end its boycott, including receiving a £3.3 billion ($4.17 billion) funding boost and measures it said would strengthen the union.

The lawmakers gathered at Stormont, Northern Ireland’s parliament in Belfast, on Saturday appointed former DUP leader Edwin Poots as speaker. 

The DUP’s Emma Little-Pengelly was appointed as deputy first minister, and said in a speech that the day’s events confirm “the democratic outcome” of the 2022 election.

O’Neill’s appointment wouldn’t have been possible prior to the 1998 Good Friday Agreement, which ended decades of nationalist-unionist conflict by ensuring both would be represented in the power-sharing government. Even then, unionists continued to appoint the first minister, a continuation of their in-built political dominance when Northern Ireland was created in 1921. 

But the picture has been gradually changing. Months before the 2022 vote, a census showed that Catholics — who traditionally support Irish nationalism and reunification — made up the biggest religious group for the first time. That raised profound questions for the region’s typically Protestant unionists, who insist that Northern Ireland remains firmly a part of the UK. Sinn Fein’s legacy as the political wing of the IRA adds to unionist unease.

That’s the wider political backdrop to the DUP’s protest, which critics said reflected its unwillingness to share power in a government that would reflect the region’s shifting dynamics. It also underscores the scale of the challenge to keep the power-sharing government up and running this time.

Even after the DUP agreed to end its boycott, a breakthrough that took five hours of talks in a remote location chosen to try to keep protesters away, the week has seen political parties revert to strident rhetoric.

Northern Ireland’s “electoral majority for unionism has gone,” Sinn Fein President Mary Lou McDonald, who is Ireland’s official opposition leader, said alongside O’Neill on Tuesday. With Sinn Fein leading polls in the Republic of Ireland too, it “signals a new Ireland emerging.” A united Ireland, she said, is “within touching distance.”

The pushback from unionists was immediate.

“It’s not helpful when Mary Lou McDonald comes out and goes a United Ireland is within touching distance — I don’t think it is,” said Emma Shaw, a community activist and founder of the Phoenix Education Centre, which aims to tackle educational under achievement in east Belfast. 

The British government, too, was unequivocal. Asked about Sinn Fein’s rise and the likelihood of a border poll — the mechanism for reunification set out in the Good Friday Agreement, subject to majority support for a united Ireland — the UK’s Northern Secretary Chris Heaton-Harris replied: “Not in my lifetime.”

Despite the unionist opposition, reunification “has never been as live a policy issue” as it is now, said Muiris MacCarthaigh, head of politics and international relations at Queen’s University Belfast. “It all stems back to Brexit,” he said, which put the issue of identity “firmly on the agenda.”

Brexit also exposed ructions within Northern Ireland unionism, which were laid bare again after the DUP announced it would end its protest.

It’s two years to the day since the DUP walked out of the government in protest at the Brexit deal signed between the UK and European Union, which created a de facto border in the Irish Sea to avoid creating a land border on the island of Ireland. It also handed the region hybrid status: still in the EU’s single market for goods, even as the rest of the UK departed. 

Unionist hardliners have spent months pressuring DUP leader Jeffrey Donaldson not to return to government if Brexit rules remained. Protesters gathered outside the party’s leadership meeting on Monday, and in the House of Commons some DUP lawmakers took aim at the deal he struck with the UK government.

But Donaldson was adamant that returning to power-sharing was a better option for unionists in Northern Ireland than direct rule from London. He accused his unionist critics of not wanting power-sharing at all. “Some of them live in a bygone era,” he said. “Is this really the time for unionism to turn in on itself?”

Graham Walker, a politics professor at Queen’s, said that while there’s a minority of unionists who won’t yield ground on the Brexit deal, they don’t have the numbers to derail Donaldson’s return to power-sharing.

There are also reasons to get Stormont up and running that straddle the political divide, not least the ability to spend the additional UK funding. That will come as a relief to public sector workers who haven’t received a pay rise during the lengthy cost-of-living crisis and held a mass general strike last month. 

“There is additional money now,” said Gareth Hetherington, director of the Economic Policy Centre at the University of Ulster. “Whether it is enough to see off future strikes is yet to be determined.”

The DUP’s boycott is far from the only time the devolved assembly has been curtailed. Sinn Fein has done it, including over support for the Irish language. Since it was set up in 1999 the body has sat for less than 60% of the time. 

“When it comes to any kind of contentious issue, it’s very hard to get agreement between the parties,” said MacCarthaigh. The two parties have fundamental differences on where Northern Ireland belongs and it’s “very difficult to park that,” he added.

Based on the rhetoric this week, that picture won’t change soon. Asked about working with a nationalist first minister, Donaldson told BBC Radio Ulster he sees O’Neill as a “joint first minister.” Though the first and deputy do have joint authority in Northern Ireland, the message was clear.

(Updates with Biden comment in fourth paragraph.)

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