Not for the first time, the entire European Union is waiting in trepidation to see what Ireland decides about the fate of institutional reform in the 27-member bloc. Having already once rejected the Treaty of Lisbon in a referendum, some 3m Irish voters are being asked to reconsider this week.

If they vote No again, it seems certain to kill the treaty and precipitate a new constitutional crisis in the Union. It would probably block any further EU enlargement. It would also make mockery of Ireland’s reputation as one of the most enthusiastic EU member states and one of its biggest beneficiaries.