No president in the history of our Republic has been as disorienting as Donald Trump. His goal, even before he became president, was far more ambitious than to tell mere lies. It was to annihilate the distinction between truth and falsity, to make sure that we no longer share facts in common, to overwhelm people with misinformation and disinformation. It was to induce epistemological vertigo on a mass scale.

What happened in Lafayette Square earlier this month was the most recent link in a long chain of events. To summarize: On June 1, the president sought to make a point by walking to St. John’s Church, across the park from the White House. The church has suffered some vandalism during the protests, and Mr. Trump wanted to be photographed standing in front of it, holding a Bible as a prop. But getting the president from the White House to the church — and making the walk the show of strength Mr. Trump was desperate for — required militarized security forces to clear out hundreds of overwhelmingly peaceful protesters who had gathered in Lafayette Square, to protest the killing of George Floyd in police custody. A Washington Post investigation reported that a few protesters threw eggs, candy bars and water bottles, but that security forces used smoke canisters, explosive devices, rubber bullets and horses to clear the area.

That wasn’t the coverage the president wanted, so, as Tim Miller of The Bulwark wrote, Mr. Trump’s staff and right-wing media apologists distorted facts in order to paint a different picture. They portrayed the protesters as rioters and Mr. Trump as a man of faith who was restoring peace and order.

Using the military as part of this charade was egregious enough that it caused Mr. Trump’s former Secretary of Defense, James Mattis, to take the extraordinary step of breaking his silence on the president by denouncing him as a threat to the Constitution and national unity, and it caused the nation’s top military official, General Mark Milley, the chairman of the Joint Chiefs of Staff, to apologize for taking part in the photo op in his combat fatigues. “I should not have been there,” General Milley said.

The whole thing, from beginning to end, was about creating yet another false narrative. So was the president’s Tweet earlier this week promoting the conspiracy theory that a 75-year-old man who was shoved to the ground by Buffalo police and hospitalized as a result “could be an ANTIFA provocateur.” (The elderly man’s lawyer issued a statement saying the president’s claim was “dark, dangerous and untrue.”) And so was the president’s previous Tweet several weeks before that, promoting a cruel conspiracy theory that MSNBC’s Joe Scarborough was responsible for the death of a female staffer in 2001.

This is all part of a long-established pattern. The first hours of the Trump presidency began with a demonstrable lie, when Mr. Trump, his press secretary and his closest advisers lied about the size of his inaugural crowd, photographic evidence to the contrary be damned. The point of it was to convince the public that Mr. Trump was the object of more adoration than the black president who preceded him, and to distort reality with what Kellyanne Conway famously referred to as “alternative facts.” This should have signaled — and was intended to signal — that Mr. Trump would govern in a world of his own creation, a world of make-believe.

At a fundamental level, then, the Trump presidency has been about projecting shadows on walls and asking us to believe they are real.

The president’s brazen assaults on truth were jolting at first. Today, however, we have grown accustomed to them — and to the fact that Republican officeholders have almost without exception stood behind him during the last three-and-a-half years.

Some Republicans have had no objections to how Mr. Trump has comported himself; they are thrilled to be his courtier, to earn a pat on the head or the back from the president. Many others, though, made the judgment that it was in their interest to go along to get along, that standing up to Mr. Trump would weaken them within the party and derail their political futures, causing them to lose power even before they were turned out of power. They calculated that giving voice to their consciences was not worth incurring the wrath of the Republican base. It was easier, less wearying and a lot less of a hassle to fall into line behind Mr. Trump. In one sense, of course, they were right. But doing so comes at a price.

In his extraordinary 1978 essay “The Power of the Powerless,” which has been brought up with some frequency during the Trump administration, the Czech dissident (and later president) Vaclav Havel famously refers to a greengrocer who puts in his shop window a Marxist slogan — “Workers of the world, unite!” The greengrocer doesn’t believe in the slogan, or the regime, which is built on lies. But he acts like he does, or at least abides the lies in silence. He doesn’t have to accept the lie, according to Havel; he merely needs to live within it. But what happens, Havel asked, if one day the greengrocer, among other things, stops putting up slogans merely to ingratiate himself?

“In this revolt,” Havel writes, “the greengrocer steps out of living within the lie. He rejects the ritual and breaks the rules of the game. He discovers once more his suppressed identity and dignity. He gives his freedom a concrete significance. His revolt is an attempt to live within the truth.”

There is a cost to this action, Havel acknowledges, but by doing so the greengrocer “has shattered the world of appearance, the fundamental pillar of the system. He has upset the power structure by tearing apart what holds it together. He has demonstrated that living a lie is living a lie.”

Havel goes on to point out that the greengrocer “has said that the emperor is naked. And because the emperor is in fact naked, something extremely dangerous has happened: by his action, the greengrocer has addressed the world. He has enabled everyone to peer behind the curtain. He has shown everyone that it is possible to live within the truth.”

During the Trump presidency, Republican lawmakers who know better have been putting up propaganda signs in their storehouse windows in the name of party loyalty and self-aggrandizement. The price they would pay for honesty would be much lower than that of the citizen of a totalitarian regime. It’s still not too late to take the signs down, to break the rules of the game, and to rediscover their suppressed identity and dignity.

In important respects, though, the most worrisome thing about the Trump era isn’t the president or elected Republicans; it’s the base of supporters who have shown an unbreakable devotion to the former and an eagerness to intimidate, when necessary, the latter, to keep them aligned with Mr. Trump.

Even Mr. Trump’s media enforcers know their assigned roles. If they don’t fulfill them, they recognize they will suffer the consequences: an uprising among their viewers and listeners. Dissent is simply not permitted, and if you’re a media personality who does dissent, it can be a career-killer.

The reasons the Republican base has shown such fidelity to Mr. Trump are multilayered. Many support his policy agenda and have a near-existential fear of what an ascent to power by a Democratic president would mean. Among Mr. Trump’s supporters, there is not just dislike but detestation for the left (and those feelings are reciprocated by progressives). Resentments and grievances over being the object of the left’s contempt have built up for years. The president’s supporters view him not just as their defender; they see him as their avenging angel. And on top of all that is the acute political polarization that characterizes this era. Those with a tribalistic mind-set believe that refusing to support a Republican president is traitorous. So they have stayed loyal to the president through all the carnage, all the lies, all the appeals to our ugliest impulses.

But this, too, has a cost. What Mr. Trump requires of his supporters is that they enter his world of unreality. For most people it’s too psychologically painful to acknowledge that the person they support is deeply corrupt, pathologically dishonest and brutish. Human beings feel a need to justify their defense of such a person; this can only be achieved by distorting reality, by pretending that Mr. Trump is not who he is and that facts are not what they are.

But epistemological anarchy is a mortal threat to a free nation. If there are no knowable truths to appeal to, no common set of facts we can agree on, no shared reality that binds us together, then everything is up for grabs. Justice is impossible to achieve. Might makes right.

If this trend toward political and moral chaos is going to be reversed, it will be because ordinary citizens understand the cost of it and push back against it; because they grow weary of the manipulation; because they decide that living within the truth is better than living within a lie.

Sometimes these things can be catalyzed by honorable individuals like General Mattis saying there are some lines the president should not step over or Senator Mitt Romney, who has called out the president’s ethical transgressions while the rest of his colleagues, through their near total silence, are complicit in them.

Still, for those of us who believe politics is an honorable profession that can make the world somewhat better and more just, and who at onetime believed that the Republican Party, while flawed, was an instrument for good, this is a difficult and even disillusioning time. I’m not cynical enough to give up on politics, since the human cost of doing so is much too high. But I’m not naïve enough to deny that grave damage has been done to our nation and our politics, and, especially, to the Republican Party.

Earlier I alluded to Plato’s allegory of the cave. In the story, Plato imagines that a prisoner in the cave, who had been chained with the others, escapes to the outer world. Initially he is blinded by the sun but then he adjusts. He can see the beauty of the world, the sky and the stars. Previously he had been looking only at phantoms; now he is nearer to the true nature of being. Even so, Plato asks, “Will he not fancy that the shadows which he formerly saw are truer than the objects which are now shown to him?”

Donald Trump’s supporters have been looking only at phantoms. There is still time for more of them to see the world as it is, to be dazzled by the sunlight, to live their lives in accord with truth. Plato knew that everybody would not make this choice. But everybody should.

Peter Wehner, a senior fellow at the Ethics and Public Policy Center, served in the previous three Republican administrations and is a contributing Opinion writer, a visiting professor at Duke and the author of The Death of Politics: How to Heal Our Frayed Republic After Trump.