WASHINGTON -- As the saying goes, you don't miss the water until the well runs dry: This deeply aberrant presidency threatens to cost the nation much more than even some of Donald Trump's harshest critics may realize.

From 1988-1992, I was The Washington Post's correspondent in Buenos Aires, covering all of South America. It was a time when countries such as Argentina, Brazil, Peru and Chile -- emerging from years of authoritarian rule -- were struggling to re-establish democratic norms, and I learned one important lesson: It's easy to lose the habits and values of democracy, but incredibly hard to get them back.

Perhaps most difficult of all is to recover lost faith in the rule of law. That is why Trump's very public desire to use the legal system as a weapon against his political opponents is so damaging. "Lock her up" is more than a call to imprison Hillary Clinton. It is, potentially, a tragic epitaph for the consensus view of our legal system as a disinterested finder of fact and dispenser of justice.

In the countries I covered, military rulers had imprisoned, exiled and assassinated their internal foes. It was understandable that democratically elected governments would struggle -- sometimes successfully, sometimes not -- to find ways to hold the murderous generals and admirals accountable. Decades later, however, the pattern still persists.

Democratically elected presidents such as Cristina Fernandez de Kirchner of Argentina and Luiz Inacio Lula da Silva of Brazil have been hit with serious criminal charges since leaving office. Alberto Fujimori of Peru was extradited from Chile, tried and imprisoned for years before the current president pardoned him on humanitarian grounds. In the United States, we do not seek to jail our out-of-power leaders. Trump, with his repeated calls for the Justice Department to go after Clinton, is determined to establish the custom.

Those former leaders were charged not just with political offenses but also with corruption -- another bad habit that Trump is trying to instill.

In most of the South American countries I covered, transparency was a joke. Public officials were assumed to be in the pocket of some special interest -- rewarded not just with campaign donations but with secret offshore bank accounts and the occasional suitcase full of cash. I reported on a coup in Paraguay that was led by a general -- a lifelong public servant -- who, even before seizing the presidency, had built himself a mansion that looked like a replica of the Petit Trianon palace at Versailles.

Trump and his family have refused to divest themselves of their businesses or even draw more than a flimsy veil between their official actions and the impact those actions have on their personal finances. Does the administration's policy toward Panama really have nothing to do with a bitter dispute over the Trump-branded hotel in Panama City? Does the administration's tough new attitude toward Qatar really have nothing to do with that nation's refusal to invest in Jared Kushner's debt-laden real estate company?

It's not the potential answers to those questions that are so corrosive; it's the questions themselves. As in many countries whose governance we scoff at, Americans must now wonder whether policy is being tailored for our leaders' personal gain.

When the rule of law and financial probity can no longer be assumed, the vacuum is filled with conspiracy theories. The president himself is a conspiratorialist par excellence; he was, after all, the chief purveyor of the birther nonsense. Since neither his words nor those of his press office can be believed, it is natural -- but incredibly damaging -- to assume that the (BEG ITAL)real story(END ITAL) is being hidden from us, for reasons that must be nefarious.

During my years in Buenos Aires, every once in a while some renegade military officer would make a pathetic attempt to stage a new coup; once, when I called home at the end of a long reporting trip, my wife matter-of-factly advised that from the airport I take the long way to our house because a would-be generalissimo was blocking the shortcut with a bunch of tanks, making traffic simply a mess.

I came to cherish the long American tradition of civilian control of the military. Now we are forced to rely on three generals -- Defense Secretary Jim Mattis, chief of staff John Kelly and national security adviser H.R. McMaster -- to keep an ignorant and impetuous president from rashly triggering Armageddon.

Despite his recent joke about making himself president-for-life, Trump won't be around forever. But the damage he is doing will remain -- and it may take years of hard work to repair.

(c) 2018, Washington Post Writers Group