With his poll numbers down on just about every issue—the economy, inflation, even immigration—Donald Trump is reverting to one of his greatest hits: the ostensibly deplorable state of crime in blue cities. He’s deployed National Guard troops to Washington, D.C., and is threatening to send more to places like Chicago, Baltimore, and Los Angeles. Of course, blue-state governors like Gavin Newsom and JB Pritzker are seizing the chance to position themselves as fighters taking on Trump, even as the issue remains a potential liability for Democrats. Yes, murder rates have declined, but 81 percent of Americans, per a recent AP poll, believe crime is a “major problem” in big cities. (“Another 80-20 issue Democrats get wrong,” as the N.R.C.C. put it in a press release blasting out the poll results.)