The past year, 2018, has been a difficult one for the DUP. Which means it has been a difficult year for all of unionism.
In December 2017 Arlene Foster was confident enough to boast of the "union being secure" because of the DUP's parliamentary deal with the Conservative Party. A year later she is accusing Mrs May of a betrayal that "undermines the constitutional integrity" of the union and threatening to withdraw the votes of the DUP's 10 MPs.
During the EU referendum in 2016 the DUP was fairly relaxed. It opted for Leave, as it had done in the 1975 referendum, yet was fairly sure that Remain would carry the day.
The DUP’s old rivals in the UUP decided, “on balance”, to support Remain; so the DUP played the uber-unionist card, making their pitch around a strong, sovereign, independent United Kingdom.
It allowed them to portray the UUP as weak liberals and, in so doing, make the DUP more welcoming for another raft of UUP voters (Foster cut her teeth in the UUP and was still held in high regard by elements within her old party).
The unexpected general election in 2017 and the DUP's new role as kingmaker changed the game
The unexpected victory for Leave had the potential to make life difficult for the DUP, particularly since the North recorded a 56 per cent vote for Remain.
Special circumstances
Yet Sinn Féin was prepared to work with Foster and the UK government to ensure a deal that recognised the special circumstances in the North; and at that point, the summer of 2016, there was every reason to believe the Irish Government and EU negotiators, along with the British and the the North's executive, would be involved in a joint talks process aimed at a "soft-landing" Brexit.
The unexpected general election in 2017 and the DUP’s new role as kingmaker changed the game.
The DUP put all of their eggs into the Conservative basket, trusting Mrs May to protect them. But, like Edward Heath, Margaret Thatcher and John Major before her, she chose the “national interest” over the interests of the North’s unionists.
Not only did she support a backstop which could have led to the North being treated very differently to the rest of the UK; she also suggested that not supporting it would threaten the union: “People do not want a hard border. And if this House cares about preserving our union, it must listen to those people because our union will only endure with their consent.”
Uncertain brexit
“Those people” include business, civic and professional classes in the North who are worried by the impact of a hard or uncertain Brexit, or no deal at all.
It includes small-n nationalists and small-u unionists who value membership of the EU and who may now be prepared to listen to the case for Irish unity.
So, does Mrs May have a point? Is there a threat to the union?
It includes increasing numbers of mainstream nationalists (1,200 have signed two letters to Leo Varadkar) who fear that their rights and identity will be compromised if the UK leaves the EU. It includes that demographic in the North which describes itself as “other” and is attracted by a broader European identity.
So, does Mrs May have a point? Is there a threat to the union?
Judging by the language of the DUP, UUP, Orange Order, smaller unionist parties and spokesmen linked to former loyalist paramilitaries, they believe there is. They are more worried at the moment than I have seen them since the 1985 Anglo-Irish Agreement.
The big difference now, of course, is that the margins between unionism and nationalism are much narrower and some pro-union elements can’t automatically be banked in the anti-Irish unity lobby.
Awkward questions
Plus, the fact that a prime minister the DUP has propped up for 18 months seems prepared, in their eyes, to put the union at risk, raises some very awkward questions for unionism generally about whom they can trust to promote and protect their interests.
The real challenge could come in the form of a Border poll, provision for which is made in the Belfast Agreement.
Unionists console themselves with the belief that the terms under which the poll would be called (the North’s secretary of state needs to conclude that victory for Irish unity is likely) are unlikely to be met anytime soon.
But Brexit has upended the local dynamics; opinion polls indicate growth for unity in the event of a hard Brexit or no deal; unionists no longer have a majority in the Assembly; and, as I noted earlier, there has been a shift of opinion in the small-n, small-u and “others” demographics. In other words, the “likely” threshold required for a poll is closer than most unionists think.
Uncharted waters
What they have in their favour, though, is that the British and Irish governments are likely to have enough on their plate over the next few years without a referendum which would – even more so than Brexit – be hugely toxic, divisive and potentially dangerous.
Also, there is no substantive evidence, yet, that the Irish Government and political establishment has any particular interest in playing the unity card.
The lesson of the past 30 months for unionists is that they need to tread extremely carefully. They are in uncharted waters and facing challenges, particularly demographic ones, which they neither anticipated nor prepared for.
This is not 1912, 1974 or 1985: they do not have a sizeable, guaranteed majority to shore them up. They cannot take it for granted that a Conservative government – even with another leader – will prioritise the concerns of the North’s unionists over broader “national” interests.
Put bluntly, they need less grandstanding and red lines and more attention paid to the people in their own electoral backyard: “those people” required to sustain the union.
Alex Kane is a commentator based in Belfast. He was formerly director of communications for the Ulster Unionist Party