LONDON — President Biden heaped praise on it, as did the prime minister of Ireland, Leo Varadkar. Britain’s Labour Party threw its support behind it. Even hard-line Brexiteers in the British Conservative Party, who were expected to revolt against the agreement, swiftly fell into line.
Only one group has so far refused to support the trade deal for Northern Ireland that Prime Minister Rishi Sunak and the European Union announced on Monday: the Democratic Unionist Party, or D.U.P., which represents unionist voters in the North, who seek to remain part of the United Kingdom.
The D.U.P.’s lonely reluctance speaks not only to the devilishly complex nature of trade in the post-Brexit era but also to the deeper dysfunction of politics in Northern Ireland, which has not had a functioning government since early last year, when its fragile experiment in power-sharing last fell apart.
The Democratic Unionists say they need time to study the fine print of Mr. Sunak’s deal, known as the Windsor Framework, before they render a verdict. The D.U.P. has no legal power to hold up the agreement. But if the party rejects it, it could sabotage efforts to restart Northern Ireland’s government, one of Mr. Sunak’s key objectives in settling the trade dispute with the European Union.
And the unionist party faces a dilemma in getting to yes. Ever since Brexit, it has defined itself by its opposition to the Northern Ireland Protocol, a complicated set of rules resulting from Brexit that take account of the North’s status as part of the United Kingdom, but one that shares a border with the Irish Republic, a member of the European Union.
The protocol, the D.U.P. claims, has driven a wedge between Northern Ireland and the rest of the United Kingdom. It has deprived people in Belfast of British-made sausages, required them to file onerous paperwork to transport pets from London to Derry, and left European courts in charge of their laws.
“The D.U.P. have encouraged the view that the Protocol is the top priority and a clear and present danger to the future of Northern Ireland,” said Katy Hayward, a professor of politics at Queen’s University in Belfast. “It is difficult for them now to say to their supporters that they should accept this compromise.”
Mr. Sunak has signaled that he plans to press ahead, even without the support of the D.U.P. He has a comfortable Conservative majority in the Parliament, and there is little evidence of a mutiny in the Tory ranks.
Still, as the flagship party of Northern Ireland’s unionist voters, the D.U.P. can stymie the formation of a government. It triggered the collapse of the last government by pulling out of Parliament in January 2022 and vowing that it would not go back until the problems with the Protocol were fixed.
Civil servants have kept the day-to-day machinery of government grinding. But the political paralysis has led to a pileup of nearly 40 major funding decisions that require the approval of Stormont, the territory’s assembly. These range from improved cancer treatments, to payments to families of victims of the violence known as the Troubles, according to a list compiled by the Belfast Telegraph.
The lack of a functioning government has deepened the cynicism of the public, even sowing doubts about the durability of Northern Ireland’s hard-won peace. The United States and others have urged the North’s parties to restore the power-sharing government because it is a key legacy of the Good Friday Agreement, which ended decades of sectarian violence in the North and marks its 25th anniversary next month.
If the D.U.P. accepts the deal, it removes the party’s reason for refusing to take part in the government. But that raises another problem: For the first time in its history, it would not get to name a first minister. Sinn Fein, the Irish nationalist party, won the most seats in Northern Ireland’s legislative elections last May, giving it the right to name the first minister; the D.U.P. would have to settle for naming a deputy first minister.
As a practical matter, there is little distinction between these posts. But they are laden with symbolism in a place where Catholics recently overtook Protestants in population. Nationalists, who favor Irish unity, are predominantly Catholic, while unionists, who favor staying in the United Kingdom, are predominantly Protestant.
“If Sinn Fein is kept out of having a first minister, if we have no institutions for a long time, that will encourage frustration among nationalists,” Professor Hayward said, adding that it could trigger a renewed push for unification of the North and South.
Successive Conservative governments in London, she said, had failed to reckon with this delicate balance of interests in Northern Ireland. By whipping up the debate over the Protocol, in part because it was popular with the Brexiteer wing of the party, the Tories helped radicalize the unionist parties in the North on this issue, she said.
That could lead to one of the D.U.P.’s biggest fears: that it will be outflanked by more extreme unionist parties, a phenomenon that has hurt it during previous periods of upheaval. Already, Jim Allister, leader of the Traditional Unionist Voice party, said the Windsor Framework “does not live up to the overselling spin which accompanied it.”
Resistance is deeply ingrained in the D.U.P., which was founded in 1971 by Ian Paisley, a firebrand preacher who famously opposed the 1985 Anglo-Irish agreement for Northern Ireland with a simple but thunderous slogan: “Ulster says No.”
Nearly four decades later, there are signs of a split between the party’s leader, Jeffrey Donaldson, and harder-line members like Sammy Wilson and Ian Paisley Jr., a son of the party’s founder. The three all have seats in the British Parliament. On Monday, Mr. Donaldson struck a noncommittal tone in reacting to Mr. Sunak’s plan.
But Mr. Wilson later told Times Radio, “We have already identified a whole range of things that the government has claimed will happen which we now know won’t happen because we have looked at the E.U.’s explanation, we have looked at the government’s explanation, we have seen the difference.”
Some analysts argue that the Democratic Unionists should take credit for pressing the British government to seek beneficial changes in the Protocol. And younger members of the party appear eager to do that.
Gordon Lyons, 36, who served as the economy minister in the last government, said in a statement on Wednesday, “The only reason that Sinn Fein or any other party in Northern Ireland is offering views on the Windsor Framework is because of the determination and action of the Democratic Unionist Party.”
Mr. Lyons said his party would take time to “fully scrutinize” the legal text of the agreement before deciding whether to support it. The party has set out seven tests for the deal, which include ending the diversion of trade between Britain and Northern Ireland, eliminating a customs border in the Irish Sea, and giving people in Northern Ireland a say in the laws that govern them.
Even if they conclude the deal fails those tests, neither the British government nor the European Union appear interested in reopening negotiations over Northern Ireland. Both sides hailed the agreement as a turning of the page. Mr. Sunak is eager to get on with repairing the British economy before he has to face voters sometime in the next two years. The European Union is weary of endless squabbles over Brexit and preoccupied by greater threats like Russia’s war in Ukraine.
“The problem for the D.U.P. is that they’re between a rock and a hard place,” said Jonathan Powell, who, as chief of staff to Prime Minister Tony Blair, helped negotiate the Good Friday Agreement. “If they don’t accept it, they’re really going into a dead end. ”