Suddenly, it has become easy to see how the euro — that grand, flawed experiment in monetary union without political union — could come apart at the seams. We’re not talking about a distant prospect, either. Things could fall apart with stunning speed, in a matter of months, not years. And the costs — both economic and, arguably even more important, political — could be huge.

This doesn’t have to happen; the euro (or at least most of it) could still be saved. But this will require that European leaders, especially in Germany and at the European Central Bank, start acting very differently from the way they’ve acted these past few years. They need to stop moralizing and deal with reality; they need to stop temporizing and, for once, get ahead of the curve.

I wish I could say that I was optimistic.

The story so far: When the euro came into existence, there was a great wave of optimism in Europe — and that, it turned out, was the worst thing that could have happened. Money poured into Spain and other nations, which were now seen as safe investments; this flood of capital fueled huge housing bubbles and huge trade deficits. Then, with the financial crisis of 2008, the flood dried up, causing severe slumps in the very nations that had boomed before.

At that point, Europe’s lack of political union became a severe liability. Florida and Spain both had housing bubbles, but when Florida’s bubble burst, retirees could still count on getting their Social Security and Medicare checks from Washington. Spain receives no comparable support. So the burst bubble turned into a fiscal crisis, too.