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Opinion writer

Since he began his campaign in 2015, Donald Trump has insisted — and based a good deal of his agenda — on the notion that illegal immigrants are causing a massive crime wave. When he first came down that golden escalator, he declared, “When Mexico sends its people, they’re not sending their best. They’re not sending you. They’re not sending you. They’re sending people that have lots of problems, and they’re bringing those problems with us. They’re bringing drugs. They’re bringing crime. They’re rapists.”

Well, if illegal immigrants are causing a crime spree, you need the wall, you need to punish cities (“sanctuary cities”) that aren’t devoting resources to rounding up nonviolent illegals, and you need to kick out “dreamers” (who Trump seemed to suggest were indistinguishable from gang killers) — according to Trump and his virulently anti-immigrant advisers and congressional cheerleaders.

But of course the number of illegal immigrants, by the time he became president, had already been declining. And that crime wave? Not so much crime after all, it turns out. In the New York Times, Jeff Asher reports:

The murder rate in the United States in 2018 is on track for the largest one-year drop in five years.

The numbers obviously aren’t final, and the F.B.I. won’t formally report 2018’s murder figures until September 2019.

But based on a comparison of 2017 data and 2018 data for 66 large American cities (population over 250,000), we can observe the trend as it is occurring and offer a reasonable forecast. . . . In the cities in which data is available, murder has been down about 7 percent on average this year relative to the same point in 2017.

Former attorney general Jeff Sessions had incessantly pointed to a small bump in murders in 2015 and 2016, despite plenty of evidence this was a momentarily blip associated with specific cities. That’s exactly what the 2014-2017 blip turned out to be. And those cities Trump likes to bash? “So far this year, murder in Chicago is down 17 percent in 2018 relative to 2017, accounting for about a third of the drop in the sample. Murder is also down substantially in cities like Baltimore; Charlotte, N.C.; Louisville, Ky.; and Memphis, which all experienced large rises in murder from 2014 to 2016/2017,” Asher writes.

If you think immigration policy and crimes are linked, the data would tell you that “sanctuary cities” that focus on building community support and on violent criminals, rather than doing Immigration and Customs Enforcement’s work, made a wise choice.

You’d think facts like these would be enough to convince voters that illegal immigrants aren’t threatening their safety. (And yes, immigrants on average are less likely to commit crimes than native-born Americans.) Facts, however, are not Trump’s strong suit, nor are they sufficient to cancel out the nonstop vilification of immigrants his base watches day after day on Fox News (when the latter isn’t vilifying Robert S. Mueller III).

Logically, there is no need for a wall (other security measures are working and more funding for border personnel and judges, like those needed to address the current influx of asylum claims would be far more effective), nor for pestering cities to divert resources from catching violent criminals to rounding up nonviolent illegal immigrants. Logically, dreamers are precisely the type of immigrants — vetted for criminal records, brought here by no fault of their own, fully integrated into American society, in school or the military or working — you’d want to protect.

However, Trump’s invocation of illegal immigrants and his exaggerated and distorted portrayal of our border security issues have never been fact-based. They are fear-based. They are what fuels much of Trump’s support. They are inseparable from his political success. Acknowledging that the problem isn’t a national emergency and isn’t the most important threat to Americans' safety would be to acknowledge that the entire Trump phenomenon is based on lies, thinly disguised excuses for xenophobia and racism. Don’t then expect Trump to declare victory. What would he say to his cultlike followers if they came to believe illegal immigrants are really low on the list of challenges the United States faces?