…if any one euro zone country were to start exiting the euro, there would be bank runs on the other fiscally ailing countries. The richer European Union nations know this, and so they are toiling to keep everyone on board. But that conciliatory approach creates a new set of problems because any nation with an exit strategy suddenly has enormous leverage. Ireland or Portugal [or Greece!] need only imply that without more aid it will be forced to leave the euro zone and bring down the proverbial house of cards. In both countries, aid agreements already are seen as a “work in progress,” and it’s not clear that the subsequent renegotiations have any end in sight, because an ailing country can always ask for a better deal the following year.