ML-Implode News - The Euro's Next Existential Crisis

So long as at least one of the four rating agencies judges Portugal to be worthy, its government debt remains eligible to participate in the ECB's bond-buying program. But if the country drops to sub-investment grade at all four, the ECB's own rules forbid it from buying any more Portuguese government securities -- purchases which have ballooned to almost 15 billion euros ($17 billion) in the program's one-year lifetime... if DBRS lowers the nation's grade... it could trigger a renewed crisis in the euro area.
The ECB's purchases are arguably responsible for keeping Portugal's 10-year borrowing cost at an average of a bit less than 3 percent in the past six months. Compare that with Greece, which doesn't qualify for ECB assistance and has had an average yield of almost 9 percent since October, and it becomes clear how valuable ECB eligibility is -- and how financially damaging it might be for Portugal if it was shut out after a downgrade.

Relevant:

The Euro's Next Existential Crisis