British Prime Minister Rishi Sunak¡¯s government is beginning its hardest sell: convincing skeptical Northern Irish politicians to back its new post-Brexit deal on trade with the European Union. That means one final effort before the U.K. can finally repair relations with its biggest trading partner.

Monday¡¯s unveiling of the Windsor Framework featured a confident Sunak and a smiling, enthusiastic European Commission President Ursula von der Leyen. The next, crucial stage of the process will be a game of detail, numbers and political arm-twisting.

Sunak¡¯s team now needs to win over a tiny caucus of Northern Ireland¡¯s unionist politicians and an influential group of pro-Brexit MPs from his own Conservative Party. Failure could mean a need to push the deal through with support from the opposition Labour Party ¡ª a move that could be politically damaging for Sunak.