{D} onald Trump’s apparent imperviousness to scandal and early primary victories all but guarantee him the Republican nomination. Given President Biden’s extreme unpopularity, it’s entirely possible that Trump will be sworn in come January. We should work to understand the political and economic ramifications as soon as possible. One question looms large: What will happen to workers if a “tariff man” returns to the White House?

While much of the Trump 2.0 agenda remains unclear, the candidate and his allies have been perfectly candid about their plans for international trade. Trump himself promised a 10 percent tariff on all imports. Ostensibly this is supposed to help American workers. But even if we ignore other legitimate concerns, such as diminished economic growth and creeping political cronyism, it’s far from certain that making imports costlier will benefit America’s labor force.

We can use the core economic toolkit of price theory to explore this question. Everyone agrees tariffs will raise prices for imports, including for intermediate goods that American firms use to produce output domestically. For example, many home-country manufacturers use imported steel, which Trump’s steel tariffs made more expensive. Let’s focus specifically on the effects on labor.

Continuing with the steel example, firms respond to higher prices in two ways. First, and most obviously, they substitute away from imported steel and use more domestic steel. This is the effect that protectionists cheer. But they stop their analysis too soon. Will this substitution effect result in firms hiring more workers? The answer depends on whether steel and workers are complements or substitutes. Both are theoretically possible, but the former is far more likely. Somebody needs to work the line. We expect higher steel prices to lower the firms’ demand for labor.

There’s also a scale effect: By altering production volume, firms can better cope with the higher cost of steel. It’s technically possible for the firm’s marginal costs to fall when steel gets more expensive. Hence the firm will produce more output — and it will use more labor to do it. This effect is counterintuitive, but the Chicago Price Theory authors do a good job of explaining it. Suppose a ditch-digging firm is currently using men with shovels. If “shovels get more expensive . . . the firm switches to digging with an excavator machine.” Expanding the scale of the operation helped our entrepreneurial diggers economize on the costlier input. Similarly, firms conceivably could respond to higher foreign-steel prices by boosting volume, which they achieve by hiring more workers.

Once again, this glimmer of hope for team tariff quickly vanishes. It’s almost impossible for broad categories of inputs, such as labor, to exhibit this effect over large ranges of output. The most likely outcome is that firms scale back, resulting in lower labor demand. “Tax steel, hire more steel workers, expand output, repeat!” is an underpants-gnomes theory of political economy: A few plausible steps followed by a dash of suspended disbelief, ending in an improbable wish.

Economic data confirm these bleak prospects. Phil Gramm and Don Boudreaux recently demonstrated that steel tariffs may have increased employment in some domestic steel firms, but this was vastly outweighed by unemployment effects elsewhere. The tariffs likely cost on net more than 70,000 manufacturing jobs. Let’s not forget the comically titled opinion piece the Wall Street Journal published in early 2020: “I Support Trump’s Tariffs but Need an Exemption.” Even domestic steel producers use imported steel as an input. Protectionists’ promises are merely the latest example of that frightening saying: “I’m from the government, and I’m here to help.”

This isn’t the last word on protectionism, of course. We need to consider a host of related economic and political goals, including national security. Nevertheless, it’s revealing that this limited analysis shows that the argument for tariffs stumbles at the first hurdle. If even manufacturing workers are hurt, how much worse will things be for ordinary families, international competitiveness, and economic resilience?