ATHENS — It seemed almost too good to be true: For months, relative stability had returned to Greece, and fears that the country would exit the euro had faded like a bad dream. But a political firestorm that ignited here last week after Prime Minister Antonis Samaras dared to fire a swath of once-untouchable civil servants may threaten to undo all that.

On Monday, Greece faced the most serious political crisis since Mr. Samaras took power exactly a year ago. After issuing an order last week to immediately close the state-run Hellenic Broadcasting Corp. — setting off a wave of protests and sympathy strikes — his government coalition narrowly avoided unraveling, at least for now.

Whether or not that happens — and Mr. Samaras may yet find a resolution with his governing partners and skirt the temptation to call an early election — the latest drama underscores how instability continues to plague the government despite a growing narrative among European leaders and in financial markets that Greece is turning a corner.

On Monday night Mr. Samaras was forced to face down the members of his fragile coalition, who were seeking to reverse a decision that some of them have called an authoritarian maneuver designed to keep Greece in the good graces of its much-despised creditors.