The first sign that something was afoot with the leader of Northern Ireland’s largest pro-British party, the Democratic Unionist Party (DUP), came late on Thursday evening when all Jeffrey Donaldson’s social media accounts and his official website were deleted without comment. By Friday lunchtime, the Police Service of Northern Ireland confirmed that Donaldson had been charged with non-recent sex offences. A 57-year-old woman, widely named as his wife, has been charged with aiding and abetting in connection with the alleged offences.

The timing of the charges verges on the surreal. It is less than two months after the DUP allowed Northern Ireland’s governing multi-party power-sharing Executive to be restored, two years after it collapsed, and under a Sinn Féin First Minister for the first time ever. The return to government was contentious both within the DUP and in wider Unionist circles, where there is still deep unhappiness at the post-Brexit arrangements agreed by the UK government and the EU.

Since the return to government, the DUP has been showing its most moderate and pragmatic face to Northern Ireland’s electorate. Just this week, Donaldson was photographed smiling at a Holy Week event in Belfast involving a Catholic priest, something that would once have been anathema to the party’s fundamentalist Protestant base. DUP ministers in the Executive have also had themselves photographed trying out hurling and Gaelic football with youth teams, sports with a long association with Irish Republicanism — and considered almost as heretical as Catholicism to Ulster’s religious Right.

Party strategists were aware that its electorate nowadays includes more pragmatists than fundamentalists, and these were getting restive at the long suspension of government while the region’s public services crumbled. They were also aware that Northern Ireland’s long-term future will be decided by moderate swing voters in any future border poll — most of whom would never consider voting for the DUP and who were increasingly starting to see Northern Ireland as a failing state.

Donaldson is a member of the House of Commons rather than the Northern Ireland Assembly, so at least in the immediate term the Executive’s survival is not threatened. The DUP’s leader there is Emma Little-Pengelly, deputy First Minister, from the party’s less religious and more moderate end. She is unlikely to want to risk early Assembly elections, so the government show at Stormont is almost certain to remain on the road.

Another sign that moderates remain in pole position inside the DUP, at least for the moment, is that ultra-moderate East Belfast MP Gavin Robinson was selected as interim leader by the party’s officers before the announcement about Donaldson had even been made public.

Yet Robinson’s own electoral predicament demonstrates how threats to the DUP and the political settlement may sprout quickly in just a few months’ time. Robinson won his seat by barely 1,800 votes in 2019 and NI political anoraks think boundary changes have shaved several hundred votes off that. He is not the only DUP MP defending a modest majority.

The UK General Election was already expected to be difficult for the DUP before this announcement. The political environment for the party just became more challenging.