Spain's King Juan Carlos signs a document in Zarzuela Palace paving the way for his abdication. (Spanish Royal Palace via Associated Press)

The Spanish King Juan Carlos announced today his intention to abdicate, paving the way for the coronation of his son, Crown Prince Felipe. The increasingly unpopular Juan Carlos has weathered pressure to step down for the past year. My colleague Terrence McCoy rounds up the damning scandals that underlay the monarch's decision, including a son-in-law charged with embezzlement and his own unfortunate decision to go elephant-hunting in Botswana.

The king's departure after nearly four decades on the throne follows two other prominent European abdications: that of the Dutch Queen Beatrix and Belgium's King Albert II last year. In these "bicycling monarchies," as the FT cutely labels the two, elderly royals bowed out without much fuss, allowing the succession of younger and supposedly more capable heirs. In the Netherlands, the royal family is a ceremonial irrelevance. Its equivalent in Belgium carries only slightly more meaning, offering something of a unifying balm over the country's notorious linguistic divisions.

Europe's dozen surviving monarchies are mostly fusty, toothless institutions. European royals ski and spawn gaudy weddings; they are not scepter-waving potentates in any real sense. The Booker Prize-winning novelist Hilary Mantel likens them to pandas, "expensive to conserve and ill-adapted to any modern environment." (The map below charts the remaining monarchies around the world — see a few corrections to it here.)

royals-1024x506

What set Juan Carlos apart was that for some time he genuinely mattered. A Bourbon scion, tied to a centuries-old imperial history, he helped shepherd Spain's democratic transition from the dark years of Francoist dictatorship. His opposition to a military putsch in 1981 defined him as a monarch who — unlike other relatives who collaborated with strongmen and juntas — would not stand against the winds of change.

But the crises that have since clouded his legacy are even more telling. They involve lifestyles of excess, allegations of graft and an increasing image problem in a country ravaged by unemployment and the wages of austerity. While Europeans living in constitutional monarchies still look favorably on their royals, a growing number of them want tax funds directed to these families cut and royal salaries trimmed.

Across the continent, a new generation of princes and princesses have been at pains to style themselves as frugal, ordinary citizens. But this betrays a weird tension: If the royals are just like anybody else, why do they need to exist? Ordinary citizens are not blessed with a divine right to kingship. Ordinary citizens do not exist on public expense. It's the monarchs' role to be living anachronisms. But can Europe afford that?

The one saving grace for royal families in Europe is that ire at elected politicians is far higher. The results of the E.U. elections held two weekends ago proved that there's overwhelming distrust of political elites drawn to Brussels and the larger utopian, liberal project they champion. Far-right parties appealed to various streaks of provincial populism throughout the continent, some particularly xenophobic and intolerant. In this context, monarchies represent a pleasing, unobjectionable cultural connection to a shared national past. But it helps to remain out of the limelight.

The existential challenge facing Europe's royals seems most acute in Spain. Not only is the institution of the monarchy mired in controversy, but its ability to be a force for national unity is also in doubt. In the years since the 2008 global financial crisis, the red-yellow-purple flag of the Spanish republican movement has been a ubiquitous symbol at mass anti-austerity protests. Moreover, Juan Carlos has been staunchly opposed to the secessionist campaign in Catalonia, but it gained steam while the king's own star waned. Despite opposition in Madrid, the Catalan regional government said it will go ahead with a referendum in November.

The king's abdication will probably not be Europe's last. It's rumored that after Britain's Queen Elizabeth II eventually passes, her son Prince Charles may abdicate in favor of his son Prince William. One wonders how many more generations of costumed royals will have to ponder the same choices.