A S IF REVOLT on both wings of her own Conservatives were not enough, Theresa May faces rebellion from the Northern Irish party that props up her government. Because the prime minister lost her majority in the election she unwisely called in June 2017, she was forced into a “confidence and supply” agreement with the Democratic Unionist Party. The DUP’ s ten MP s promised to vote with the government on confidence matters, Brexit and the budget in exchange for a bung of £1bn ($1.3bn) extra spending in the province.

The deal was widely criticised. A former Treasury permanent secretary noted that the DUP had “previous” when it came to extracting bribes from Westminster. Until two weeks ago the party was at least reliably delivering its votes for Mrs May. Since she unveiled her Brexit deal, however, that reliability has come into question. This week the party exerted its power by abstaining or even voting with the opposition on amendments to the finance bill.

The DUP ’s gripe is the Northern Irish “backstop” in the Brexit deal. This would bind the province more tightly into EU single-market rules than the British mainland. The party’s leader, Arlene Foster, says this breaks Mrs May’s promise that, after Brexit, Northern Ireland will not be treated differently from the rest of the United Kingdom and there will be no border in the Irish Sea. She is not reassured by Mrs May’s response that there will be no customs controls and no new regulatory barriers to Northern Irish exports to the mainland. For that leaves open the idea of extra regulatory checks, however discreetly they may be done, on goods that go from Britain to Northern Ireland.

After the DUP ’ s finance-bill rebellion, the Labour opposition crowed that the confidence and supply agreement was over and Mrs May’s government was “in office but not in power”. Yet the DUP was careful not to cause fiscal damage and says the agreement is not dead. More problematic for Mrs May is its threat to vote against the Brexit deal when it comes to the Commons next month. With as many as 70-80 Tory MP s also promising to vote the deal down, the extra DUP votes seem to doom any chance she may have had of winning parliamentary approval for it.

Like the Tory rebels, the DUP is demanding that Mrs May renegotiate the Brexit withdrawal agreement, which includes the backstop. Yet it is clear that the EU is not prepared to reopen the legal text of that agreement. This week it was fleshing out the accompanying political declaration about future relations, giving countries like France and Spain the chance to raise grievances about fisheries and Gibraltar, respectively. Changes to the declaration at the EU summit due on November 25th could make it even harder for Mrs May to win approval for the deal at home.

The government has not given up on winning over the DUP . Over half the £1bn bung remains to be spent, after all. And though the party hates the Brexit deal, there are things it may dislike even more. It would not welcome a no-deal Brexit that led to a hard border in Ireland. It does not support a new referendum on Brexit. And it certainly does not want political chaos that could lead to another election. That could not only end its powerful position backing Mrs May’s government but also put into power Labour’s leader, Jeremy Corbyn, whom unionists see as an inveterate republican sympathiser.