The 2016 presidential campaign has defied expectations at almost every turn, but it has produced one seemingly immutable fact: The Establishment is a spent force.

Lurking behind this simple truth, however, is a whole collection of puzzles. Is the death of the Establishment mostly an event in presidential politics, or does it apply to the entire American political system? Or is it a broader event with deep roots in society at large?

And perhaps even more important, what exactly is the Establishment in the first place? The politicians and journalists who have become addicted to the term don’t stop to explain what they think it actually means. The more we trouble to think seriously about the Establishment’s demise, the more problematic the whole subject becomes.

When most of us imagine the existence of an establishment in a presidential campaign year, we conjure up visions of a small group of party leaders meeting in private, reaching agreement on who their presidential nominee is going to be and making it stick. This form of establishment is indeed gone, but it didn’t die this year, or in any recent election cycle. It has been dead for more than half a century.

If the Establishment is indeed a cohesive cadre of high-level decision-makers, then the last time it genuinely functioned was in 1952, when an elite group of East Coast lawyers, financiers and diplomats anointed Dwight Eisenhower as the Republican presidential nominee, and an equally exclusive cohort of Democrats chose Adlai Stevenson as his opponent. Neither man had to run for the job -- he just had to accept the offer. That’s how you can tell an establishment is at work.

Nothing like that has happened in decades. Jimmy Carter, Bill Clinton and Barack Obama, the last three Democratic presidents, all entered as insurgents bent on crashing through the barriers to political leadership, not as favorites seeking to succeed by elite anointment. George W. Bush had plenty of influential Republican friends in 2000, but he still had to fight his way through a bruising and often brutal primary season. Mitt Romney looks and sounds like the epitome of what an establishmentarian is supposed to be, but he too had to claw his way to the nomination in 2012. Nobody gave him anything.

Of course, the problem could lie in the definition. Maybe, instead of conjuring up smoke-filled rooms, we should think about establishments more broadly as clusters of voters and political actors who live in suburbs, work in the higher echelons of corporate America, follow the dictates of the Chamber of Commerce, and generally believe in preserving the social and economic status quo. By that measure, establishmentarianism continues to exist, at least in the Republican Party.

But if that’s what the Establishment is, I’d still argue that it hasn’t exercised much clout in the presidential nominating process for quite a while now. Most of the Republican candidates who have become household names in the last 60 years -- Barry Goldwater, Richard Nixon, Ronald Reagan -- carried a chip on their shoulders when it came to the supporters of the status quo. Having close ties to the Establishment hasn’t been anything to brag about in presidential politics for a very long time. Those who have succeeded have managed to portray themselves as outsiders in some tangible or symbolic way. George H.W. Bush professed to love pork rinds. His son managed to acquire the cadences of a Texas oil-field accent.

Nevertheless, that hasn’t stopped the political commentariat from looking around every four years and proclaiming the decline of the Establishment as if it were something new. Journalists are a little bit like the Bill Murray character in the movie Groundhog Day: They keep waking up to the same music and failing to realize they’ve heard it before. It’s not a perfect analogy -- Murray eventually figures out what’s going on -- but it captures the essence of the situation. All Donald Trump has done is turn up the volume on the radio.

But this Groundhog Day peculiarity doesn’t just infect presidential campaigning. It’s a force practically everywhere in American politics.

Consider state legislatures. Anybody sent to cover one in the 1950s or ’60s, or a bit later in some places, had the privilege of observing a classic establishment at work: a close-knit group of elected and unelected leaders making all the important decisions and essentially imposing them on the membership at large.

Each state was a little different, but there were some elements common to most of them. The leading legislators socialized together in cliques that did their most crucial work during off hours and in private, usually in favored bars or restaurants. House speakers and Senate presidents tended to remain in power for many years. A disproportionate number were from rural communities, because the malapportionment of seats gave rural parts of the state outside influence. Key members mixed with lobbyists in a nearly seamless web of political influence. It was a cabal of pragmatists; ideologues were rarely invited to join. Newly elected members weren’t listened to very much; it took a few terms for a legislator to win the Establishment’s trust.

You still see freshman legislators vowing to take on the Establishment and reporters filing stories asserting the decline of entrenched power, but in most places they are several decades behind the curve. With a few notable exceptions, such as Illinois and New York, concentrated legislative authority fell victim to “one person, one vote,” to the decline of seniority, to the increased presence of women legislators, to the modest tightening of ethics and disclosure rules, and to the refusal of most junior members to sit quietly for a few years and do as instructed. The Establishment died out in state politics around the time it collapsed in presidential campaigning, and for some of the same reasons.

Back when state legislatures were governed by cabals of senior legislators, local governments were dominated by establishments of a different sort. In a few big cities, the Establishment meant a single party boss who had control of the nominations in the party that dominated local affairs. This was the “Daley Machine” model from mid-century Chicago that still resonates even among some Americans too young to have experienced it. In most cities, the Establishment wasn’t a single power broker but a close-knit alliance of party insiders who dictated key policy decisions to rank-and-file city council members and compliant mayors.

In smaller communities that had adopted city manager government, often in disgust at political machines and party bosses, a different sort of Establishment prevailed. Generally it consisted of the manager, a handful of trusted city bureaucrats and a friendly collection of business leaders. They often made the important political and policy choices over breakfast or lunch in a café conveniently located near city hall or the county courthouse. I have literally never come across a community of any size that didn’t have a political café of this sort in the 1950s and 1960s.

Why have I made the leap from presidential campaigning all the way down to the bottom rungs of government? Because in their heyday, all levels of American politics operated in roughly the same fashion. They were managed by an establishment that decided who the officeholders in their jurisdiction should be. Whether the power brokers were financiers on Wall Street or Rotary Club members in a small Midwestern town, they all understood what their job entailed. It was their duty to sift through the ranks of aspiring candidates and choose which ones were capable and reliable enough to hold the important offices within their territory. They were looking for people who had paid their dues -- and could be depended upon to keep paying them even after they had won the prize of political office.

When this system collapsed in the late ’60s and early ’70s, it fell apart from top to bottom, from the upper reaches of presidential politics to the tedious slate-making choices in small-town diners. Establishments gradually ceased to function as judges of political integrity and talent. Upstarts crashed the gates of the political process, winning elections as presidents and governors, and for myriad minor offices further down.

Who chose these people? They chose themselves. I wrote that in a book 25 years ago, but I didn’t foresee that it would apply even more forcefully to the politics of 2016 than it did to those of a generation ago. The idea of self-nomination is helpful in explaining Jimmy Carter, Bill Clinton and Barack Obama; it is even more helpful in explaining Donald Trump.

Why the Establishment declined is a question that can’t be answered fully in a single column. Perhaps it will suffice as a start to say that over the course of the ’60s and ’70s, Americans lost the confidence and trust they once felt toward authority in almost every walk of life. There are many casualties of that disillusionment, but one of the important results has been a refusal to let an establishment of any sort choose political leaders through a process of anointment. If you follow that disillusionment from its beginnings in the ’60s to the present, you end up with Donald Trump. He may seem like a radical break from the past, but in many ways he is the culmination of a process that began more than half a century ago and has yet to play itself out.