It’s important to acknowledge when you’ve been wrong, and I’ve probably never been so wrong as I was in an op-ed published on April 13, 2010. At the time, I was stunned by a terrible tragedy: the crash of a plane that had carried the Polish president, Lech Kaczynski. He had been flying to the Russian city of Smolensk to visit the memorial at Katyn, where Stalin murdered 20,000 Polish officers in 1940. Several dozen senior military figures and politicians were also on the plane, many of them friends of mine and colleagues of my husband, who was then the Polish foreign minister. Among them was his deputy, Andrzej Kremer, a wonderful man and brilliant diplomat.

In the sweep of emotion that followed the crash, comparing the event to Katyn, I wrote this sentence: “This time around, nobody suspects a conspiracy.” As an excuse, I offer the fact that the tragedy initially seemed to bring people together. Politicians of all parties, from right to left, had been on the plane. Widely attended funerals were held across the country. Even Vladimir Putin, then the Russian prime minister, seemed moved. He arranged for the broadcast of “Katyn” — an emotional and very anti-Soviet Polish film — on Russian state television as a kind of memorial. Nothing like it has ever been shown so widely in Russia, before or since.

But my optimism was premature. The president’s brother, Jaroslaw Kaczynski, then the unpopular leader of the parliamentary opposition, seems to have initially believed, as all the evidence has always shown, that the crash was an accident. Then he changed his mind. Perhaps he could not accept that his beloved twin had died randomly, in a pointless crash. Perhaps he was maddened by grief. Perhaps he felt guilty: He had helped plan the trip. Or perhaps, like Donald Trump, he saw that a conspiracy theory could help bring him to power.

Much as Trump used birtherism to inspire his core voters, Kaczynski, in the years that followed, used the Smolensk crash to motivate his supporters, that minority of the Polish population that remains convinced that unnamed secret forces control the country, that the “elite” is manipulated by foreigners and that everything that has happened in the country since 1989 is part of a sinister plot. And it worked. Last year, thanks to flukes of the electoral system, less than 40 percent of the vote — reflecting 18 percent of the adult population — proved sufficient for his nationalist-populist party, Law and Justice, to win a slim parliamentary majority.

Readers familiar with my recent op-eds will know that I am not shy about pointing out Russian plots when I see them. But there is just no evidence of one at Smolensk. Within hours of the crash, Polish forensic experts were on the ground. They immediately obtained the black boxes and transcribed them meticulously. The cockpit tape can be heard online, and it makes the circumstances painfully clear. The president was late; he had planned a live broadcast from Katyn. When Russian air traffic controllers wanted to divert the plane because of heavy fog, he did not agree. The chief of the air force sat in the cockpit during the final minutes of the flight and pushed the pilots to land: “Be bold, you’ll make it,” he told them. According to the official report, written by the country’s top aviation experts, the plane hit a tree, then the ground, and then broke up.

Donald Trump’s campaign praises the Republican presidential nominee for ending the ‘birther’ controversy while his Democratic opponent Hillary Clinton says he must apologize to President Obama. (Bastien Inzaurralde/The Washington Post)

In the wake of Trump’s grudging renouncement of birtherism, the insidious, racist theory that gave rise to his political career, it’s worth pondering what happened when Law and Justice came to power. Within days of taking office, the new government removed the official report from its website. (It’s still available online.) More recently, police and prosecutors entered the homes of the aviation experts who testified in the original investigation, interrogated them and confiscated their computers.

A new (and well-paid) government commission was formed, containing a group of cranks and “experts” — including an ethnomusicologist, a retired pilot, a psychologist and other people with no knowledge of air crashes. The defense minister, Antoni Macierewicz, who is obsessed with conspiracies of all kinds — famously, he has given credence to the Protocols of the Elders of Zion, an infamous, Czarist-era anti-Semitic forgery — has floated multiple theories, many of which contradict one another. Sometimes the previous Polish government is blamed, sometimes Putin. Sometimes there has been an explosion, sometimes a deliberate controller error. Sometimes “the government,” which was of a different party than the president, is said to have sabotaged a trip that in fact was prepared by the president’s office. None of these theories has ever been accompanied by the slightest hint of genuine evidence.

Because they have been unable to disprove the original report, the ruling party instead ordered the creation of a fake version of reality in the form of a film. “Smolensk” came out two weeks ago and purports to show the “true story” of the crash and the “coverup.” The conclusion — it involves an onboard explosion — is so preposterous that some viewers have howled with laughter. Nevertheless, the film has been declared “true” by Kaczynski, and the education minister has suggested that schoolchildren ought to see it. As in communist Poland, a fictionalized version of history, one that suits those in power, could eventually be on the curriculum.

In due course, there may be other consequences. One of the first things Law and Justice officials did upon taking power was launch an open attack on Poland’s constitutional court, and to re-politicize the independent prosecutor’s office. At the same time, they have put all of the country’s secret services in the hands of a man who has been convicted of fabricating documents, and whom they then pardoned. They might have had many motives for making these changes. But if nothing else, they could use these tools to “prove” one of the ludicrous theories using faked evidence at public show trials, another communist innovation. That kind of drama might satisfy Kaczynski emotionally; he might also reckon it would help him politically.

I realize that there is far more detail here about Poland than most non-Polish readers care to know. But I’m offering it for a reason. Trump, like Kaczynski, pushed a patently false conspiracy theory hard for many years, despite the utter lack of evidence. Last week, he found it expedient to discard that theory, but once he is president, he might find it expedient to adopt it again — or perhaps to push one of the many others he has championed. As president, he can then use the state — the Justice Department, the security bureaucracy, the FBI — to pursue them. A Trump administration could make birtherism the excuse for fake investigations, hearings and even trials that would do terrible and irreversible damage to U.S. politics and the rule of law.

It all sounds unthinkable, of course. But if you’d asked me five years ago, or even one year ago, I would have told you that the transformation of the Smolensk conspiracy theory into state ideology was unthinkable, too. And yet it has come to pass.

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