Thomas Frank in The Guardian.

Let us now address the greatest American mystery at the moment: what motivates the supporters of Republican presidential candidate Donald Trump?

I call it a “mystery” because the working-class white people who make up the bulk of Trump’s fan base show up in amazing numbers for the candidate, filling stadiums and airport hangars, but their views, by and large, do not appear in our prestige newspapers. On their opinion pages, these publications take care to represent demographic categories of nearly every kind, but “blue-collar” is one they persistently overlook. The views of working-class people are so foreign to that universe that when New York Times columnist Nick Kristof wanted to “engage” a Trump supporter last week, he made one up, along with this imaginary person’s responses to his questions.

...Last week, I decided to watch several hours of Trump speeches for myself. I saw the man ramble and boast and threaten and even seem to gloat when protesters were ejected from the arenas in which he spoke. I was disgusted by these things, as I have been disgusted by Trump for 20 years. But I also noticed something surprising. In each of the speeches I watched, Trump spent a good part of his time talking about an entirely legitimate issue, one that could even be called left-wing.

Yes, Donald Trump talked about trade. In fact, to judge by how much time he spent talking about it, trade may be his single biggest concern – not white supremacy. Not even his plan to build a wall along the Mexican border, the issue that first won him political fame. He did it again during the debate on 3 March: asked about his political excommunication by Mitt Romney, he chose to pivot and talk about ... trade.

It seems to obsess him: the destructive free-trade deals our leaders have made, the many companies that have moved their production facilities to other lands, the phone calls he will make to those companies’ CEOs in order to threaten them with steep tariffs unless they move back to the US.

Trump embellished this vision with another favorite left-wing idea: under his leadership, the government would “start competitive bidding in the drug industry.” (“We don’t competitively bid!” he marveled – another true fact, a legendary boondoggle brought to you by the George W Bush administration.) Trump extended the critique to the military-industrial complex, describing how the government is forced to buy lousy but expensive airplanes thanks to the power of industry lobbyists.

From Leiter, who calls it "An interesting take... (though it can't be the whole story)"

"working class, "middle class"

middle class, working class, workers, upper class, managers, management

Fox tried to arrange a Trump Sanders debate. Sanders agreed, but Trump pulled out.

Frank

Trade is an issue that polarizes Americans by socio-economic status. To the professional class, which encompasses the vast majority of our media figures, economists, Washington officials and Democratic power brokers, what they call “free trade” is something so obviously good and noble it doesn’t require explanation or inquiry or even thought. Republican and Democratic leaders alike agree on this, and no amount of facts can move them from their Econ 101 dream.

To the remaining 80 or 90% of America, trade means something very different. There’s a video going around on the internet these days that shows a room full of workers at a Carrier air conditioning plant in Indiana being told by an officer of the company that the factory is being moved to Monterrey, Mexico and that they’re all going to lose their jobs.