Last night at the Republican presidential debate in Houston, Texas, the tables were turned on Donald Trump. For once, he became the target of sharply worded criticisms and a few insults rather than being the only one dishing them out at debates. Rather than let the reality star define them, his major opponents, Marco Rubio and Ted Cruz, did their best to hold him accountable for his record on a host of issues like support for elements of socialized medicine and neutrality about the Middle East.

Even worse for the frontrunner, Rubio played Trump’s game by directing personal scorn at him in a way that might do him more harm than proving that he is advocating liberal stands on a variety of topics. Those who are susceptible to Trump’s charms may not be willing to think about the policy implications of electing a man whose stands are, in many respects, indistinguishable from those of Hillary Clinton. But the phrase “con man” — with respect to his hiring of illegal foreign workers to construct his iconic Trump Tower or the fraudulent “university” that bears his name may stick.

The impact of this turnabout has yet to be seen and the loyalty of Trump’s fan base may be so strong that nothing about him, his positions or his past would be enough to shake their faith in the idea that he is the nation’s savior. In an election in which a critical mass of voters believe the expression of anger as well as nostalgia for the past when America was “winning,” are the only legitimate positions to take, a logical dissection of Trump’s empty slogans may be falling on deaf ears.

Nevertheless, it is perhaps time to take a closer look at Trump’s favorite talking point: His promise to build a wall along the nation’s southern border and to make Mexico pay for it. That line is so popular it has even become a chant at his rallies.

The question as to how Mexico could be compelled to pay for the wall hasn’t bothered Trump’s fans too much. Mexico has made it clear that they won’t pay a dime for such an edifice with one former president delivering that answer with profanity that inspired Trump to respond last night with a hypocritical condemnation of his language

But faced with repeated demands to explain how the Mexicans will pay, Trump has finally volunteered an answer. It’s simple he tells us. The U.S. has a trade deficit with Mexico. How exactly he will use that deficit to extract tens of billions out of the Mexican republic is left a big vague, but we’re supposed to think that the billionaire will leverage this fact of economic life into a huge windfall for the United States.

That’s might be enough of an explanation for the Trump fan base which seems to think that Trump’s deal-making skills are a magical power rather than a function of economics. But let us dignify Trump’s claim with at least a moment of reflection.

Trump is right that there is a trade deficit between the U.S. and Mexico. The U.S. Census Bureau’s statistics show it be at $58.3 billion for 2015. In 2014, the deficit was $53.8 billion.

When stated in isolation that can strike American voters as an outrage. It is, of course, a function of lower prices and wages in Mexico that makes it cheaper to manufacture goods that are then sold in the U.S. Since the underlying factor motivating much of Trump’s popularity is both a strident nationalism as well as a touch of xenophobia about immigrants, attacking trade deficits is a natural for the candidate.

But trade is, by definition, a two-way street, not a gift or payment between nations. It is one thing to attempt to redress such a deficit by measures aimed at leveling the playing field when one nation behaves unfairly. It is quite another to imagine that it can be converted into a payment like the cash rewards offered by some credit cards. The only way to create a massive reversal of the trade deficit with Mexico is to put a tariff on goods crossing the border. By that means, Trump might very well be able to create a fund of billions that could pay for a wall or anything else he’d like to build.

But while putting a tariff on products creates revenue for the state levying the tax, it also raises the prices of the goods in question. Which is to say that the price of the $294.7 billion in Mexican goods that are sold in the United States will go up. Moreover, that will also trigger a Mexican response in the form of a higher tariff on the $236.3 billion in items manufactured in the United States that are sold in Mexico.

That is what is called a trade war and while Trump may have expressed no fear about having one in last night’s debate, the many millions of Americans that buy Mexican goods or that manufacture those sold south of the border won’t be as enthusiastic.

So strip away the boasts and the reality star’s nationalistic chest thumping and all you’re left with is a policy that will hurt consumers and manufacturers on both sides of the border. More to the point, what it means is that Mexico won’t be paying for the wall. You don’t have to be an economist to understand that it is American consumers and workers that will actually be the ones who will pay the price for Trump’s vow; not the Mexican government.

By seeking to hurt trade, Trump is playing to the fear and the pride of American voters. He’s also seeking to transform the Republicans from a party that has stood for free enterprise, free markets and free trade that will grow economies to a protectionist faction that resembles the left wing of the Democrats more than Ronald Reagan’s GOP.

But more important than that, Trump’s pay wall boast is just another version of Trump University, a con game that swindles suckers into thinking they’re getting a free lunch when in fact the only one profiting will be the Donald. If Republicans buy into this scam, they can’t claim they weren’t warned.