The Small Party Threatening to Topple Theresa May’s Government

LONDON—British Prime Minister Theresa May has faced her fair share of resistance over Brexit: from the opposition Labour Party, from the Euroskeptics within her ruling Conservatives, and even from members of her own cabinet. But the latest rebellion isn’t just from the usual suspects. Now, it’s coming from the small Northern Irish party that is propping up May’s government—and it could bring the whole government down.

Arlene Foster, the leader of Northern Ireland’s Democratic Unionist Party (DUP), issued a to May’s government following her visit with European Union negotiators last week. Foster reaffirmed that her by U.K. and EU negotiators in December to prevent the implementation of a hard border between Northern Ireland and the Republic of Ireland in the event the U.K. and the EU fail to achieve a future trade deal. Ideally, negotiators hope, the plan will never need to be used.