This is an archived article that was published on sltrib.com in 2016, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.

WASHINGTON • There are many things about this election that, a year ago, would have seemed not only improbable but also downright preposterous: the tremendous popularity of a self-described socialist, the number of news cycles devoted to euphemisms for candidates' genitalia, etc.

But perhaps the most improbable aspect of this highly improbable election is this: Of all possible issues, trade — trade! — has become the economic centerpiece of the 2016 presidential campaign.

"TPP," a once-esoteric initialism for the Trans-Pacific Partnership, gets shouted out at campaign rallies. This week Donald Trump gave an entire speech on trade — his most compelling, coherent policy talk yet — at a plant near Pittsburgh. Subsequently Hillary Clinton and Bernie Sanders spent the rest of the week trying to prove they care about trade way more than Trump does. They cared about trade before it was cool!

Usually trade makes voters' eyes glaze over. It hasn't been a central, salient issue in presidential campaigns for about two decades, when it took a star turn in Ross Perot's "giant sucking sound" anti-NAFTA campaigns.

Since then, it's barely been a peripheral issue. For understandable reasons.

The big structural changes to our economy from trade, and accompanying job losses, mostly happened a long time ago, in the decades following World War II.

For all its controversy, even the North American Free Trade Agreement had relatively little effect on U.S. employment, according to studies from the Congressional Research Service, Organization for Economic Cooperation and Development, and others. Subsequent bilateral trade deals have likewise had negligible effects.

The amount of trade that the United States engages in has grown over time, but even today trade remains a small share of our economy, at least relative to most other countries.

That's not to say that the Americans displaced by trade — millions of factory workers who lost their jobs over the decades, for example — have recovered. Hollowed-out Rust Belt towns reveal persistent unemployment and great suffering. And the United States never did right by these trade victims; one of the implicit promises of earlier trade deals was that the winners would compensate the losers, which never happened.

But the fact remains that U.S. trade's losers are a small, and shrinking, share of the workforce. Meanwhile, the winners are widespread. Contrary to Trump's and Sanders' claims about the benefits of trade accruing to only a few rich elites, trade's benefits in the United States are quite diffuse, affording a wide swath of consumers a better quality of life through cheaper and more varied products.

The losses from trade tend to be felt by a small, concentrated group.

More to the point, that small, concentrated group has become less and less politically significant over time.

Research from Craig VanGrasstek, a trade historian, has linked declining trade-related propaganda in presidential campaigns to the shrinking number of swing states that still have significant shares of their population (at least 0.25 percent) in key manufacturing industries.

"It no longer makes sense to win electoral votes by promising protectionism," VanGrasstek told me, because there just aren't that many purple-state voters who still have a stake in the issue.

Finally, the most puzzling thing about trade's renaissance as a campaign issue is that all remaining presidential contenders have positioned themselves as roughly on the same side. There's not much ground left to fight over.

So how exactly did trade talk get its groove back?

One possible explanation: When Americans talk about "trade" today, we're not really talking about trade. Rather, "trade" has become a scapegoat for other economic forces and policy choices that have increased inequality, and a proxy for ethnic tensions and white anxiety about loss of social status.

It's telling that when presidential candidates argued about trade in the olden days, they were talking about industry-specific protections. In the 2012 and 2016 elections, VanGrasstek noted, politicians have largely focused on country-specific protections. Trump in particular often talks about "losing" to some faceless group of foreigners, especially nonwhite ones with "funny" accents.

Anti-immigrant rhetoric, closely intertwined with anti-trade rhetoric, also emphasizes problems with (nonwhite) illegal immigrants from Mexico — even though the United States has had a net outflow of Mexican immigrants lately, and the country whose citizens are most likely to illegally overstay their visas in the United States is (majority-white) Canada.

Trade-as-proxy-for-some-other-hot-button-issue is not exactly a new development, of course. Trade policy has experienced mission creep for decades, used to shape human rights, national security, environmental and other not-exclusively economic concerns.

Perhaps we shouldn't be surprised that it's shapeshifting again into an outlet for other American anxieties.

Twitter, @crampell