As sheriff of Maricopa County, Ariz., Joe Arpaio engaged in blatant racial discrimination. His officers systematically targeted Latinos, often arresting them on spurious charges and at least sometimes beating them up when they questioned those charges. Read the reportfrom the Justice Department’s Civil Rights Division, and prepare to be horrified.

Once Latinos were arrested, bad things happened to them. Many were sent to Tent City, which Arpaio himself proudly called a “concentration camp,” where they lived under brutal conditions, with temperatures inside the tents sometimes rising to 145 degrees.

And when he received court orders to stop these practices, he simply ignored them, which led to his eventual conviction — after decades in office — for contempt of court. But he had friends in high places, indeed in the highest of places. We now know that Donald Trump tried to get the Justice Department to drop the case against Arpaio, a clear case of attempted obstruction of justice. And when that ploy failed, Trump, who had already suggested that Arpaio was “convicted for doing his job,” pardoned him.

By the way, about “doing his job,” it turns out that Arpaio’s officers were too busy rounding up brown-skinned people and investigating President Barack Obama’s birth certificate to do other things, like investigate cases of sexually abused children. Priorities!

Let’s call things by their proper names here. Arpaio is, of course, a white supremacist. But he’s more than that. There’s a word for political regimes that round up members of minority groups and send them to concentration camps, while rejecting the rule of law: What Arpaio brought to Maricopa, and what the president of the United States has just endorsed, was fascism, American style.

So how did we get to this point?

Trump’s motives are easy to understand. For one thing, Arpaio, with his racism and authoritarianism, really is his kind of guy. For another, the pardon is a signal to those who might be tempted to make deals with the special investigator as the Russia probe closes in on the White House: Don’t worry, I’ll protect you.

Finally, standing up for white people who keep brown people down pleases Trump’s base, whom he’s going to need more than ever as the scandals creep closer and the big policy wins he promised keep not happening.

But the Trump base of angry white voters is a distinct minority in the country as a whole. Furthermore, those voters have always been there. Fifteen years ago, writing about the radicalization of the G.O.P., I suggested the hard core of angry voters was around 20 percent of the electorate; that still seems like a reasonable guess.

What makes it possible for someone like Trump to attain power and hold it is the acquiescence of people, both voters and politicians, who aren’t white supremacists, who sort-of kind-of believe in the rule of law, but are willing to go along with racists and lawbreakers if it seems to serve their interests.

There have been endless reports about the low-education white voters who went overwhelmingly for Trump last November. But he wouldn’t have made it over the top without millions of votes from well-educated Republicans who — despite the media’s orgy of false equivalence or worse (emails!) — had no excuse for not realizing what kind of man he was. For whatever reason, be it political tribalism or the desire for lower taxes, they voted for him anyway.

Given the powers we grant to the president, who in some ways is almost like an elected dictator, giving the office to someone likely to abuse that power invites catastrophe. The only real check comes from Congress, which retains the power to impeach; even the potential for impeachment can constrain a bad president. But Republicans control Congress; how many of them besides John McCain have offered full-throated denunciations of the Arpaio pardon?

The answer is, very few. Paul Ryan, the speaker of the House, had a spokesman declare that he “does not agree with this decision” — not exactly a ringing statement. Yet Ryan did better than most of his colleagues, who have said nothing at all.

This bodes ill if, as seems all too likely, the Arpaio pardon is only the beginning: We may well be in the early stages of a constitutional crisis. Does anyone consider it unthinkable that Trump will fire Robert Mueller, and try to shut down investigations into his personal and political links to Russia? Does anyone have confidence that Republicans in Congress will do anything more than express mild disagreement with his actions if he does?

As I said, there’s a word for people who round up members of ethnic minorities and send them to concentration camps, or praise such actions. There’s also a word for people who, out of cowardice or self-interest, go along with such abuses: collaborators. How many such collaborators will there be? I’m afraid we’ll soon find out.