He understands human nature better than most. He knows how we like to blame our problems on external forces, how indifferent the elites can be to working-class struggles, and the strain that immigration and trade can place on low-skilled American workers who feel besieged and displaced. He also understands how to cynically mix together those ingredients, add a dash of fear with racial undertones, and whip up a magic stew capable of transporting a carnival barker to the White House. 

But the president has much to learn about the history of NAFTA.

He’d better study up fast. Last week, the Trump administration formally notified Congress of its intent to renegotiate the agreement. While it’s unlikely that Americans will ever see a brick-and-mortar wall on the U.S.-Mexico border, Trump is well on his way to keeping at least one campaign promise.

In a letter to congressional leaders, U.S. Trade Representative Robert Lighthizer said that the administration wants NAFTA to be “modernized.”

I’m worried that “modernized” is Trump-speak for “gutted.”

Now, the meter is running. In less than 90 days, the United States can start renegotiating the agreement with its partners -- Mexico and Canada. The idea is for Congress and the White House to spend these next three months conferring about how to change NAFTA in order to benefit American workers. 

Trump is convinced -- probably because he says it so often -- that NAFTA is unfair to Americans. He has it backward. 

NAFTA should in fact be renegotiated -- because it has traditionally been unfair to Mexicans. 

Consider the illuminating example of Mexican trucks, which were largely kept off U.S. roadways -- in violation of NAFTA -- during much of the Clinton and Obama years. 

This was all to please the Teamsters. You see, union truck drivers don’t want to compete with Mexican drivers for lucrative long-haul contracts in the United States, even if the jobs originate in Mexico. And they have the political muscle to make themselves a monopoly. 

So, for years, U.S. drivers benefited from this crazy system where Mexican trucks were barred from going beyond 25 miles of the U.S.-Mexico border. Mexican truckers would have to pull over and transfer their cargo onto U.S. trucks, which would then complete the journey to cities like Milwaukee, Seattle or St. Louis. 

That’s not fair, and it’s harmful for commerce. How do unions defend something like that? Technically they don’t have to. That’s why they line the pockets of Democratic politicians, who then make the argument for them on the House floor or Senate chamber. 

And that’s where things got ugly. In the immigration debate, it’s usually Republicans who flirt with racism and demagoguery to serve their narrow political interests. But in the debate over NAFTA, and the Mexican trucks, it was Democrats who played that game as they shamelessly attempted to camouflage their errand for the unions as a public-safety issue. 

All through the 1990s, Americans were told how rickety and unsafe these Mexican trucks were, and how Mexican drivers were likely hauling drugs or were themselves operating under the influence of drugs. The idea was to scare Americans into maintaining the 25-mile prohibition -- despite the fact that people living in U.S. border communities such as Brownsville, Texas, or San Diego shared their highways with Mexican trucks every day and never had much trouble.

President Obama finally lifted the ban and granted the Mexican truckers permanent access to U.S. roadways, but that didn’t happen until January 2015. That was more than 20 years after NAFTA went into effect. By then, Obama was closing out his second term and no longer had to worry about carrying water for the Teamsters and labor unions. 

Now there’s a fear that Trump will use the NAFTA renegotiation to scrap that order, and take us back to the dark days of the Clinton administration. If Trump succeeds in running Mexican trucks off U.S. roadways, how strange would that be? A Republican president adopting the pro-union protectionist policies of a Democratic predecessor. 

It makes you wonder. Democrats are implying that Trump works for Russia. We should be asking if he really works for them.