The Spanish philosopher Jose Ortega y Gasset  wrote many brilliant books before his death in 1955, but his most famous book still is pertinent almost a century after it was written in 1928.  Its title is The Revolt of the Masses, and it chronicles in elegant Spanish prose (which translates well into English) a long-term pattern in human behavior beginning with the Renaissance in Europe and culminating in post-World War I Western civilization – namely, the gradual and unrelenting coming to power of the masses as they overthrew the ancient institutions of feudal and imperial rule.

What makes The Revolt of the Masses so remarkable is its prophetic account of the rise of totalitarian fascism and communism.  Ortega predicted in 1928 the rise of Hitlerian Nazism and Stalinist communism, and the consequences, well before these totalitarian upheavals murdered tens of millions of persons and violently disrupted the lives of hundreds of millions more.

Ortega, for all his prophetic brilliance, had his intellectual shortcomings, and they have led to his decline as a universally acclaimed figure in modern thought.  He was, for example, a man of aristocratic bent with many 19th-century prejudices about women and the mass of humanity.  In today's politically correct world, some of his commentary would seem archaic and tone-deaf.  He was also very much a Europhile who somehow (even as late as 1928) did not perceive the United States as the imminent world power and civilizing force it would soon become.

Ortega argued, in short, that the masses of humanity, long ruled over by feudal lords, kings, emperors, and dictators, were assuming real power in the world as they gradually overthrew authoritarian institutions.  He further argued that this "revolt" was taking two forms.  The first was "indirect" power in the form of representative democracy.  The second was "direct" power, in which societies acted through totalitarian action, often by violence, without law, without legislation and discourse, and without accountability.  It was his prophetic notice of the latter, then making their first appearances in Germany, Italy, and Soviet Russia, that worried him.  In the decade following the publication of The Revolt of the Masses, his anxieties would come all too terribly and unspeakably true.

Now, in 2016, the phenomenon of mass "disturbance" has apparently come to America – not in the pathological form of any "direct action" movement, but in the form of "indirect action" mutinies against the establishments of both major political parties.

The liberal media and political establishments thought for a while that this mutiny was limited to the other side, the conservative side, when "outsider" Donald Trump suddenly appeared and presumably won the Republican nomination for president, demolishing "political correctness" and establishment power in the process.  But this liberal smugness has now been replaced by the Democrats' own mutiny in the form of "outsider" Bernie Sanders and his wave of populism.

Whereas Mr. Trump's GOP opponents retired from the field in the wake of his upset victories in the cycle's primaries and caucuses, Mr. Sanders has refused to withdraw, even in the face of the enormous mathematical odds against his nomination.  Not only has he failed to retire, but he has won an impressive string of primary victories after the race was "declared over" by the media and the political class, including, most recently, a win in Oregon and a virtual tie in Kentucky.

His actions, designed to move the Democratic Party far to the left, apparently will be played out at the Democratic national convention in Philadelphia two months from now.  Before that, the California primary will occur in June.  This primary will send a huge number of delegates to the convention.

Mr. Trump's opponents have not been entirely inactive, either, but their efforts, almost certainly too late, will not likely change the outcome at the GOP convention in Cleveland.

The 2016 U.S. election is both a fulfillment of Ortega's insight into the long-term rise of the masses and a rebuke to his anxiety about the strength and persistence of representative democracy.

After it occurs, history is easy to explain.  But before it happens, it almost always produces surprises.