Now that the German elections are over, the euro zone needs to get back to crisis fighting. And top of the list of urgent problems is what to do about Portugal.

Uniquely among crisis countries, Portugal has seen no benefit from improving sentiment toward the euro zone. Despite second-quarter growth in gross domestic product of 1.1%—the strongest in the currency bloc—Portuguese 10-year government bond yields have soared well above 7% from 5.23% in May. Last week Lisbon was warned by Standard & Poor's that its credit rating...