Sean O'Grady: If Spain fails, it will be too expensive to save

The working assumption throughout the financial crisis is that Greece, Ireland and Portugal are all "manageable" – even in the worst case scenarios they are simply too small to threaten the existence of the eurozone by exhausting its resources. Spain, it is readily agreed, is on a different scale. As the fourth largest economy in the eurozone a potential Spanish bailout has so far been too horrible for Europe's leaders to contemplate. Her sovereign debt is spread too widely, her international trade too substantial to her neighbours; her financial system too integrated with that of Germany and France and Italy – and the UK. Let us not forget Banco Santander is now a major "British" bank that owns the old businesses of Abbey National, Alliance and Leicester and Bradford & Bingley. Like the US investments banks in the financial crisis, Spain is "too big to fail" – but also too large and costly to save.

The real question, even more urgent and crucial is whether another eurozone and IMF loan is really the answer. Many of Spain's banks, like Ireland and for that matter the UK's are busted, their bad debts are so large that they will never be able to function again. Like Portugal and Greece, Spain has a fundamentally uncompetitive labour market, though she has tried to reform it.

Unlike any of those three, Spain's unique system of devolution has left many of her provinces with far more control over public finances than Madrid – and they do not want to subscribe to further waves of austerity. For political and financial reasons, then, Spain is vulnerable, though thus far she has impressed observers with her determination to succeed. Then again, the Greek, Irish and Portuguese governments were not afraid to confront their problems, until the problems became too large for even the most courageous politician to face down.