MADRID — You know a monarchy is in trouble when the queen is jeered at the Royal Theater, of all places, and by a classical music audience. This happened to Queen Sofía of Spain last year in Madrid — a scene then repeated elsewhere with other members of the royal family.

A recent poll put support for the Spanish monarchy at a historic low: More than 60 percent of Spaniards want King Juan Carlos to step down. And all this is happening amid a series of scandals involving the royal household, the most serious of which are corruption charges against the king’s son-in-law, also involving the king’s daughter, Princess Cristina.

What is astonishing about this turn of events is that the Spanish monarchy was once deemed rock-solid. King Juan Carlos was praised both inside and outside Spain as a model monarch; the man who in the 1970s steered the country’s complicated transition from the military rule of Gen. Francisco Franco to parliamentary democracy; the king who stood up to an attempted military coup in 1981. He was said to be loved by his people, who were grateful for what he had done — and it was true.

What has changed? Not the king, but the country. Popular opinion has changed so fast and so dramatically that it is perhaps not surprising the monarchy has failed to keep pace.