Sir Jeffrey Donaldson, new leader of Northern Ireland’s Democratic Unionist party, is striving to heal DUP wounds that pose a very potent threat to its status as the region’s most powerful political force.

The 58-year-old is expected to ease internal divisions by sharing the DUP’s prized ministerial positions in Northern Ireland’s government between his supporters and those of Edwin Poots, his predecessor as party leader, who was ousted last week after just 21 days in the job.

Donaldson, named DUP leader on Tuesday, is also aiming to unite the party around the cause of aggressively pressing the UK government to overhaul contentious post-Brexit trading rules between Great Britain and Northern Ireland.

These arrangements were strongly criticised but ultimately tolerated by Poots and Arlene Foster, Northern Ireland’s former first minister. Her removal as DUP leader in April heralded what has been the most tumultuous period in the party’s 50-year history.

The urgency of forging consensus within the DUP stems from a big decision facing Donaldson: whether to endorse a first minister appointed by Poots against the party’s will, propose a replacement, or collapse Northern Ireland’s government in protest at post-Brexit trading rules.

A collapse would have far-reaching consequences beyond the DUP: the power-sharing government at Stormont established under the 1998 Good Friday Agreement drew a line under the sectarian violence in Northern Ireland that claimed more than 3,600 lives.

Shuttering the Stormont assembly could destabilise the region in the early stages of the summer marching season, which often inflames tensions between Northern Ireland’s Catholic nationalist community and Protestant unionists.

“We need Stormont established for people to see that politics is working and it’s not always in a perpetual crisis,” said Peter Sheridan, chief executive of Co-operation Ireland, a peace-building organisation. “Wherever you have a political vacuum there is always the danger of violence.”

Whatever happens in the next few weeks, Donaldson, a senior DUP MP at Westminster, knows that at the very least he is counting down to Stormont assembly elections scheduled for next May. He intends to stand in them, and then become first minister, he told the Financial Times.

But the elections will be a public test that the DUP is ill-equipped to face in its current state of disarray. One recent opinion poll put its support among voters as low as 16 per cent, compared with more than 35 per cent in the early days of Foster’s leadership.

“The DUP machine . . . is completely unfit for an election compared to how primed they usually are,” said Sophie Whiting, co-author of an award-winning book about the DUP.

Established as a hardline breakaway from the Ulster Unionist party, the DUP was for decades synonymous with its founder, the late Rev Ian Paisley. He set up his own Free Presbyterian church and was famed for quotes such as “save Ulster from sodomy” in his effort to prevent the decriminalisation of homosexuality in the late 1970s.

Diarmaid Ferriter, an Irish historian, said some of what had played out in the DUP since Paisley stepped down as leader in 2008 was typical of the “infighting after a very dominant authoritarian figure departs the stage”.

Neither of the DUP’s subsequent two leaders — Peter Robinson or Foster — had the charisma of Paisley, and internal party divisions became more pronounced.

But the fallout from the UK’s departure from the EU has also played a central role in the DUP ructions. The pro-Brexit party briefly enjoyed major influence at Westminster when it propped up Theresa May’s minority UK government, and the DUP rejected her withdrawal agreement with the EU.

But when Boris Johnson replaced May as UK prime minister, the DUP accused him of betrayal after he finalised a Brexit deal that created a customs and regulatory border between Great Britain and Northern Ireland. Treating their region differently to the rest of the UK was anathema to Northern Ireland’s unionists.

“It’s very hard for [the DUP] to explain what happened,” said Alex Kane, a longtime Northern Ireland commentator.

The DUP has also been coming under threat from the winds of change in the region. Young people, and their parents and grandparents, have begun to embrace gay rights, abortion and other issues that clashed with the DUP’s deep conservatism.

Dissatisfaction with Foster inside the DUP included a perceived softening of her stance on social issues after she failed to vote against legislation banning gay conversion therapy.

But the biggest issue for Foster was the DUP’s handling of the Northern Ireland protocol — the part of Johnson’s Brexit deal that introduced the border in the Irish Sea.

Tim Cairns, a former DUP adviser, said the criticism of Foster “wasn’t that she was too soft on the protocol, it was that she was too soft in the action she was taking to get rid of the protocol”.

Poots succeeded Foster with promises to do better on the DUP’s most important issues, and to embrace a more inclusive leadership style.

He failed at both, notably by agreeing to continue the power-sharing government involving the DUP and the nationalist Sinn Féin party on terms overwhelmingly opposed by his colleagues at Stormont and Westminster.

Poots infuriated DUP politicians by striking an agreement under which Westminster would pass legislation to protect and promote the status of the Irish language — a top priority for Sinn Féin.

Donaldson on Monday launched his bid to lead the DUP with a warning that the government at Stormont could collapse if the UK did not take “decisive action” on the Northern Ireland protocol.

A UK government official said Donaldson was seen as a “more pragmatic” figure than Poots, adding that the new DUP leader’s experience at Westminster meant he had “relationships with people” that could ease negotiations on the protocol.

Still, securing changes to the protocol will be difficult, not least because any revisions must be agreed with the EU. The British official rejected the suggestion that the UK government would have to give the DUP a sweetener on the protocol to ensure Northern Ireland’s stability.

Kane said he believed Donaldson would do everything possible to avoid a collapse of the region’s government. “He isn’t giving up Westminster and coming back to Northern Ireland just to allow the assembly to come down,” added Kane. “He wants to be first minister.”

As for the future of the DUP, while the party has been scarred by recent events, Donaldson arguably inherits a better situation than his predecessor.

In particular, Poots resolved the contentious Irish language legislation, relieving Donaldson of an issue that was always going to be problematic for some inside the DUP.

Furthermore, Donaldson is privately more progressive on social issues than he is in public, and a strategic long-term thinker, according to people who know him.

Cairns said: “There are certainly problems within the party, [but] if anybody is going to sort that out I think Jeffrey is probably best placed to do that.”