The economic direction of a Trump presidency is largely unknown and unknowable — especially, it seems, to him. His role thus far, both economically and politically, is to be a spoiler. It is as if a skunk (mephitis mephitis) had crept under the tent of the Republican nominating circus. The other acts performing under the tent (if not the spectators) have been driven to the exits.

In spite of the ensuing chaos and malodorous recrimination, Trumpus Economicus remains unabashedly if fuzzily opinionated on a range of economic subjects. Perhaps the most salient is NAFTA, for which Trump's puffing condemnation of it as a "disaster" offers a window into his peculiar modus operandi.

Like so many Trumpisms, his NAFTA narrative is remarkably Marxian (part Karl, part Groucho). This ideological reverse spin contributes to the deep dissonance surrounding the likelihood that he will be the Republican nominee.

It centers on what the right has disparaged as a Democratic theme: class warfare. As George Packer writes in the May 16 New Yorker, "Trump has seized the Republican nomination by finding scapegoats for the economic hardships and disintegrating lives of working-class whites, while giving these voters a reassuring but false promise of their restoration to the center of American life."

NAFTA works for Trump on three levels of resentment, reinforcing a smoldering sense of lost entitlement. First is the sense that but for NAFTA, good job opportunities would not have slipped inexorably into underemployment over the past 25 years. Second is that this slow decline was other peoples' fault — specifically the snooty, overeducated elites (personified by Hillary Clinton) who advocated for a neoliberal trade regime out of textbook conviction rather than shop-floor experience. Third, as told tellingly by Trump's taco bowl taunt, the jobs have been stolen by foreign enemies — Mexicans.

Facts, it is often said, are stubborn things, but probably not as stubborn as Donald Trump's devotion to his own sort of truths, which fail even the Colbert test of "truthiness." Like many crypto-Marxists, Trump is — as Packer pegs him — "a celebrity proto-fascist with no impulse control."

Consider NAFTA and jobs. When the first Bush administration entered into NAFTA negotiations in the early 1990s, the U.S. economy was 25 times the size of Mexico's. It was therefore predicable that freer trade would have at most negligible impacts on U.S. jobs. A report that I was asked to prepare at the time for a consortium of Minnesota businesses disappointed them by predicting that over 10 years, NAFTA might create 900 new Minnesota jobs.

A retrospective study from Trump's alma mater, the Wharton Business School at the University of Pennsylvania, concluded in 2014 that after 20 years, NAFTA's principal effects have been expansionary, primarily because 40 percent of U.S. imports from Mexico are derived from U.S. sources employing U.S. workers. Mauro Guillen, a Wharton management professor, observed that NAFTA has substantially ended Mexican-U.S. migration and that without it there would be many more "people wanting to come to the United States."

NAFTA, in other words, has taken the place of Trump's wall at the border.

If the Wharton professors are dismissed as neoliberal textbook believers, perhaps we might look to the nonpartisan Congressional Research Service. In an April 2015 report on NAFTA, it concluded (in line with an earlier Congressional Budget Office study) that the impacts of the agreement on U.S. economic activity worked out to "a few hundredths of a percent."

We are left to ask: Will Trump nonetheless have his way with the facts, especially if those who would confront him react with aversion to his pungent mendacity?

The Latin name for a skunk, mephitis mephitis, means "foul smell" — repeated as if for emphasis. Its natural range includes the U.S., Canada and most of Mexico. In Mexico, its name is El Zorrillo. Writing in "The Voyage of the Beagle" (1838), Charles Darwin observed: "Certain it is that every animal most willingly makes room for the Zorrillo."

We shall shortly see if the U.S. electorate does, too.

Carlisle Ford Runge is Distinguished McKnight University Professor of Applied Economics and Law at the University of Minnesota. He served as special assistant to the deputy U.S. trade representative during the Uruguay Round of multilateral trade negotiations. The opinions expressed here are his alone.