But Turkey wasn’t the target of the essay, written by Philip Giraldi. He was aiming, as his headline declared, at “Deep State America.”

Mr. Giraldi, executive director of the Council for the National Interest, a foreign-policy advocacy group in Washington, called the American deep state of today an “unelected, unappointed, and unaccountable presence within the system that actually manages what is taking place behind the scenes.”

In contrast to Turkey, where Mr. Giraldi said a covert “deep state” had taken root in the security realm, the American deep state of his description consists of visible people like the Clintons and the former C.I.A. director David H. Petraeus, concentrated around New York and Washington, who live at the fertile nexus of government and corporate power: Capitol Hill aides and legislators who cash in as lobbyists; former politicians who earn millions speaking to banks, or landing sinecures with them; technocrats who ricochet between Goldman Sachs and the Treasury Department; billionaire kingmakers dangling political donations; thinkers whose tanks are financed by corporations with a financial stake in their research.

Now if this sounds like the rant of a lefty conspiracy theorist, consider the article’s home: a magazine called The American Conservative, a contrarian thorn in the side of the establishment right.

The “deep state” metaphor seems to be ascendant as a way to explain present American realities. The writer Peter Dale Scott, professor emeritus of English at the University of California, Berkeley, last year published a similarly minded book called“The American Deep State,” which emphasized the role of security contractors, oil companies and financial firms. Meanwhile, Mike Lofgren, a Republican who spent 28 years as a congressional aide before quitting in 2011, has used “deep state” to describe a subterranean cross-party consensus on issues like “financialization, outsourcing, privatization” — a consensus, Mr. Lofgren has written, from which the public is distracted by above-ground debates over “diversionary social issues such as abortion or gay marriage.”

It is possible, and perhaps wise, to dismiss the “deep state” idea as misguided. Theories about shadowy forces are always to be taken with much salt.

Yet, as America witnesses the dual political phenomena of Donald Trump on the right and Senator Bernie Sanders on the left, and now the very public efforts by the establishment to step in and hinder either from going too far, the deep-state idea has renewed currency.

“Talk in G.O.P. Turns to a Stop Donald Trump Campaign,” read the headline in this newspaper this month. It described Republican donors uneasy with the billionaire businessman’s unorthodox, even antibusiness views on issues like trade and the taxation of financial elites. Operatives apparently felt no embarrassment in publicly declaring a consensus among party elites that “something must be done to stop” Mr. Trump, in what is supposed to be a democratic primary process.

Then came the Democratic Party companion piece, a report that its leaders, fearing the insurgency of Mr. Sanders, a self-described democratic socialist, are developing “Plan Bs” to draft into the race should Hillary Rodham Clinton falter. All the Plan Bs mentioned are white, male, graybeard Democrats who have run for president before and are far safer to corporate donors than Mr. Sanders.

Mr. Trump and Mr. Sanders have tapped into swelling populist sentiment in American life today — the former because he is a billionaire who boasts of independence from the corrupting sway of billionaires, the latter because he seeks to sharply reduce inequality.

That both men have surged in tandem this election season, against the predictions of most, is telling. What will be more telling still is how far — or “deep” — supposedly open and democratic political parties are willing to go to provide a check on democracy.