“This has been building for months but it has become pronounced recently,” he wrote in an email. The Trump administration hopes “Democrats will react by defending immigration and look ‘soft on gangs,’ ” aware that “if they push the envelope on this issue they can get coverage for their efforts and drown out Democratic efforts to change the topic.”

Brodnitz described Trump’s tactics as offering “ideas that sound really outlandish but that they believe have popular support — at least with their core voters” and that the Long Island speech was based on “the hope that Democrats would look more concerned about criminals than about crime and its victims.”

To put it mildly, it has been difficult for the Democrats to recruit key white voters to consider an economic agenda in the face of concerted efforts by the Trump campaign and his administration to shift the focus to crime.

Gallup found in October 2016 that the percentage of Americans who said they had “great respect” for the police had risen from 64 percent in 2015 to 76 percent in 2016. The poll was conducted three months after the killing of three police officers in Baton Rouge and five officers in Dallas in July and a steady barrage of headlines spotlighting Black Lives Matter, along with allegations of excessive force by police and several high-profile killings.

I asked a prominent political scientist — a man with generally moderate views — for his reaction to Trump’s comments in the Long Island speech. His answer surprised me. Requesting anonymity in order to speak candidly, he replied:

I think, yeah, a lot of people, whites anyway, think that the police are too constrained. When I watch the anarchists tear up Oakland, which happens pretty regularly, a part of me thinks “where are the 1968 Chicago police when we really need them?” These thugs behave the way they do in part because there are no consequences. Also, we see a lot of cases on TV where someone is resisting arrest, the police wrestle him down and hit him a few times, and then there are complaints about excessive force. Heavens’ sakes, if someone doesn’t comply with an order, what are the police supposed to do?

Trump made no secret of his views during the 2016 campaign, and not only received the overwhelming support of non-college white men, 71-23 (as has been widely noted), but also carried white men with college degrees by a smaller but still hefty margin, 53-39.

“Trump is endorsing the lex talionis — an eye for an eye,” Jonathan Haidt, the author of “The Righteous Mind” and a professor of ethical leadership at N.Y.U.’s Stern School of Business, wrote in an email. In his own surveys, conducted at YourMorals.org, “only a subset of people on the right endorse such beliefs; it’s basically the authoritarians, not the Burkean or ‘status quo’ conservatives.”

One question Haidt’s survey asks respondents is whether they agree or disagree with the idea that “a criminal should be made to suffer in the same way that his victim suffered.”