Members of the Democratic Unionist Party have ousted their leader, Arlene Foster. The Fermanagh-born lawyer spent more than five eventful years at the helm of the DUP but, yesterday, she announced she would leave her position by the end of May and step down as Northern Ireland’s First Minister in June. Earlier in the week, a majority of the party’s Stormont MLAs and Westminster MPs signed a letter demanding a leadership election.

According to a former special adviser in the DUP, Tim Cairns, its notoriously opaque rules require an election to take place before the 30th of April each year, but time is running out for that to happen. “Usually it’s a rather jocular rubber stamping exercise,” he explained on Twitter, “but I suspect that won’t be the case this year.”

However or whenever her replacement is appointed, it’s been a dramatic and disappointing end to the career of Northern Irish unionism’s first woman leader. When Arlene Foster took over from Peter Robinson in 2015, she appeared well placed to modernise the DUP and broaden its appeal to pro-Union voters, while retaining traditional supporters.  Not a teetotaller, not a Free Presbyterian, university educated and relaxed in modern Britain, Foster had the capacity to appeal beyond traditional unionist heartlands.

An eternity ago, at the party’s 2016 conference, enthusiastic young DUP members surrounded their leader on stage and belted out a chorus of “Arlene’s on fire” to the tune of Gala’s ‘Freed from Desire’. Unfortunately, even that piece of exuberance caused controversy, because the event took place in Belfast’s La Mon Hotel, where, in the 1970s, the IRA exploded an incendiary device and murdered twelve people in a fashion grisly even by the standards of Provo terrorism.

Mrs. Foster was soon in deeper trouble, as she became embroiled in the Renewable Heat Incentive (RHI) scandal. She was in charge of the Department of Enterprise, Trade and Investment (DETI) in 2012, when the scheme was launched without proper cost controls.

That story rumbled on through the dying months of 2016, with her successor at DETI, Jonathan Bell, giving a lurid interview to the BBC’s Nolan Show. Bell dropped to his knees on camera, asking God to help him tell the truth, before accusing DUP officials of trying to “cleanse the record” of references to Mrs. Foster’s involvement in RHI. Inevitably the BBC, with its weakness for unionist scandals outpacing its interest in anything Sinn Fein might offer by way of competition, obsessively ran this story for month after month.

Many of Foster’s DUP critics are dismayed by the party’s response to the Northern Ireland Protocol

The following January, Sinn Fein effectively ordered Foster to stand aside as first minister while the scheme was investigated. Predictably, she refused, and former IRA henchman, Martin McGuinness, resigned as deputy first minister. This solved two large problems for Sinn Fein, who had been slowly losing support from nationalist voters during the long grind of compulsory “power sharing” coalition government. They had taken fright at the insurgent left wing populist micro party, People Before Profit, who had won two MLAs at the previous Assembly election, so deep freezing the Assembly took care of that threat. And they faced a succession crisis in Northern Ireland,there was no obvious replacement for the dying McGuinness. With neither the Sinn Fein nor the IRA aspect of republicanism going large on contested leadership elections, a breathing space was very helpful in terms of finding a front of house replacement for the long time Provo.

These cynical manoeuvrings collapsed the power-sharing executive — note well that Brexit did not: Foster and McGuinness had in fact worked together in the wake of Leave winning — and the devolved institutions were mothballed for three years, as republicans made their return to government dependent on a shape-shifting list of ‘red-line’ demands. The collapse of Northern Ireland’s devolved institutions breached the Belfast Agreement, which should have prompted sanctions from Westminster. Parliament refused to take action against Sinn Fein or restore direct rule, leaving a vacuum of governance. There was no great cry of outrage from left-wing commentators about the damage republicans were doing to the ‘peace process’ by refusing to discharge their obligations under the agreement.

Many of Arlene Foster’s current critics in the DUP are dismayed by the party’s long-term limp response to the Northern Ireland Protocol, which effectively separates the province from the rest of the UK internal market and puts Brussels in charge of its economy. Other members, though, are more immediately exercised by Mrs. Foster’s recent abstention during a non-binding vote on banning “conversion therapy” for LGBT people.

This motion, tabled by the rival Ulster Unionist Party (UUP), was arguably drafted sloppily, but the visceral reaction it provoked from some parts of the DUP shows how difficult it will be for any successor to restrain its fiery, evangelical wing. When Foster looks back on her leadership, she may wonder whether she missed a unique opportunity to promote firm unionism, while avoiding self-defeating stubbornness on social issues.

After she succeeded Peter Robinson as leader, she enjoyed popularity in her party and goodwill from the public. It was already clear that the DUP could not realistically prevent measures like same-sex marriage and abortion reform indefinitely. As the debates on those issues became increasingly overheated, many younger unionists in particular expressed revulsion at the party’s ‘anti-gay’ views.

Mrs. Foster could have allowed DUP MLAs to oppose same-sex marriage, in the first year of her spell as First Minister, without triggering the Assembly’s cross community voting mechanism (the ‘petition of concern’). That might have allowed the passage of legislation bringing Northern Ireland into line with the rest of the United Kingdom, without incurring years of damage to unionism’s reputation in the eyes of younger voters and many mainland Britons.

This venal approach to the issue of who formed the national government did little to improve the DUP’s reputation

After the ignominy of RHI and the March 2017 Assembly election, when unionists lost their majority at Stormont, Mrs. Foster was offered redemption by Theresa May, who triggered a snap general election in June that year. The DUP performed much better this time and the Conservatives, who failed to gain an overall majority, needed the party’s support to stay in government.

During “confidence and supply” talks with the Tories, the party could have sought a full coalition government and genuine influence in national politics. Instead it flaunted £1 billion of extra public spending for Northern Ireland, which it claimed it had secured as the price for its support. This venal approach to the issue of who formed the national government did little to improve the DUP’s reputation as being anything other than Tammany Hall-style hucksters. A sort of British Fianna Fáil: provincial and slightly shabby.

It’s been claimed that Foster had the option of choosing to back a softer form of Brexit, or that she miscalculated by failing to persuade her party to support Theresa May’s ‘backstop’ agreement. This criticism isn’t fair. The DUP’s only ‘red line’ during the government’s negotiations with the EU was that Northern Ireland should be treated the same as the rest of the UK.

The “backstop” certainly didn’t match that requirement, as the attorney general at the time, Geoffrey Cox, confirmed. The whole point of this “insurance policy” was that Great Britain could decide at a later date to break alignment with the EU’s single market and customs union, while leaving Northern Ireland under Brussels’ auspices. Every damaging feature of the Northern Ireland Protocol was possible under the backstop, which also placed the province officially outside the UK’s customs union.

DUP MPs did associate with the European Research Group, bolstering its credentials as an arbiter of Brexit, but they didn’t get an opportunity to vote for (or against) a deal that didn’t erect barriers between Northern Ireland and Great Britain. In theory, the party might have supported even a “soft Brexit”, had that criterion been met. Theresa May failed to guide her Withdrawal Agreement through parliament because she couldn’t command enough support from her own party, not principally because of the DUP.

Ultimately, though, Foster’s spell as party leader will be remembered as a disappointment and a missed opportunity. Under her leadership, the DUP could have transcended its parochial roots, to exert real influence at Westminster and strengthen the Union. It could have advocated muscular unionism at Stormont, while accepting that society was changing in ways that it was powerless to prevent. So should not have foolishly sought to restrict its potential pool by futilely trying.

Instead, it is now worryingly uncertain which direction the DUP will take after Foster. Will it appoint a relatively unifying figure, or return to its Paisleyite roots as a party of protest? Mrs. Foster was not a successful leader, but her successor could be very much worse.