More: Consider Mid-Continent Steel and Wire, which produced roughly half of the nails made in the U.S. After the steel tariffs took effect, its sales plunged by more than half, causing it to lay off 80 workers. Another 120 quit because they worried its Missouri factory might close. After this damage, the Commerce Department granted the company a tariff exemption.

Auto makers were another casualty. Ford Motor said tariffs subtracted $750 million from its bottom line in 2018, which reduced profit-sharing bonuses for each of its workers by $750. GM said the tariffs dented its profits by some $1 billion, equal to the pay of more than 10,000 employees.

The tariffs also made U.S. manufacturers less globally competitive and prompted retaliation that hurt American businesses. Canada imposed tariffs on $12.8 billion in U.S. products, including 25% on steel and 10% on aluminum. Harley-Davidson shifted some production to Thailand to avoid Europe's retaliatory tariffs on U.S. motorbikes.

Retaliation caused Mr. Trump to exempt Canada and Mexico as part of the renegotiated Nafta deal. His Administration also struck deals with some countries that exempted a certain amount of their steel and aluminum exports.

Even so, the tariffs created uncertainty for U.S. manufacturers and boomeranged on steel and aluminum companies. Employment in durable goods manufacturing began to decline in early 2019, which reduced demand for steel and aluminum. Employment in fabricated metals manufacturing that used steel and aluminum plunged and is still some 35,000 lower than when the tariffs took effect.

U.S. steel and aluminum firms enjoyed a surge in post-pandemic investment and consumer spending, and profits rolled in. But demand for the metals fell again as U.S. manufacturing struggled amid President Biden's regulatory onslaught and higher interest rates. Domestic steel-making capacity utilization has fallen back to 70%, about the same as in 2016.

Which is why U.S. steel and aluminum producers now want tariffs with no exemptions. They blame imports for reducing prices. But steel prices are about 50% higher than pre-pandemic levels and aluminum prices a third higher. Cleveland-Cliffs shares rose 17.9% Monday, and other steel makers by 5% or so in expectation of windfall tariff profits.

This is political rent-seeking at its most brazen, and it benefits the few at the expense of the many. None of this matters to Mr. Trump, whose dogmatic views on tariffs can't be turned by evidence. But we thought our readers would like to know the rest of the story.