By THE EDITORIAL BOARD AUG. 31, 2016

It’s ridiculous that Donald Trump’s immigration proposals — not so much a policy as empty words strung together and repeated — should have propelled him as far as they have. This confounding situation hit peak absurdity on Wednesday.

It started with Mr. Trump’s meeting with President Enrique Peña Nieto of Mexico, in Mexico City. It was surreal because Mr. Trump has spent his entire campaign painting Mexico as a nation of rapists, drug smugglers and trade hustlers who would have to pay for the 2,000-mile border wall that Mr. Trump was going to build. But instead of chastising Mr. Trump, Mr. Peña Nieto treated him like a visiting head of state at a news conference, with side-by-side lecterns and words of deferential mush.

An unusually muted Mr. Trump called Mr. Peña Nieto his friend and said they had not talked about the bill for the wall; Mr. Peña Nieto later disputed that on Twitter, saying he had refused to pay. There was no friction at the photo-op, which allowed the Republican nominee to try on his calm, grown-up voice, avoid offending his nativist base and humiliate Mexico, all at the same time.

Mr. Trump then headed back over the border, shedding his decorum by the time he got to Phoenix.

In a strident speech given over a steady roar of cheers, he restated his brutally simple message: Criminal aliens were roaming our streets by the millions, killing Americans and stealing our jobs, and he’d kick them all out with a new “deportation force,” build the wall and make America safe again.

The speech was a reverie of immigrant-fearing, police-state bluster, with Mr. Trump gushing about building “an impenetrable, physical, tall, powerful, beautiful southern border wall,” assailing “media elites” and listing his various notions for thwarting evil foreigners. He said the immigration force might deport Hillary Clinton.

Which is what makes Mr. Trump’s decision to speak in Phoenix so perversely appropriate. While Mr. Trump’s plans for a locked-down deportation nation are largely a nativist fantasy, immigrant communities in Arizona have lived with the reality of what the Trump vision leads to: the brutal racial profiling and policing abuses of Sheriff Joe Arpaio, a staunch Trump ally, who echoes and inspires Mr. Trump’s vicious talk about immigrants as criminals. As Sheriff Arpaio seeks a seventh term this fall, his opponents are pushing back, with protests and get-out-the-vote campaigns, to stop the sheriff’s re-election.

Arizona, home of Minutemen vigilantes and a powerful grass-roots immigrant-rights movement, has long been a national bellwether on immigration policy. It was a fitting backdrop to Mr. Trump’s hollow proposals, and his relentless lies about the dangers that immigrants pose to the lives of “our American citizens.” Tornadoes are hollow at the center, too, and they do a lot of damage.