Put yourself in the shoes of a purchasing manager considering adding the Ivanka Trump Collection to your stores. Even if you think her products are excellent, Mr. Trump’s outburst provides an incentive not to stock them. After all, if it doesn’t work out, who wants to be in the cross-hairs of an easily angered president with 24.3 million Twitter followers and the power of the regulatory state? It might be far safer to do business with someone else.

Mr. Trump’s strategy to protect his daughter’s business seems to mirror his strategy to protect American jobs. Just as he has made it more expensive for potential partners to sever business relationships with his daughter, the C.E.O.s of Carrier, General Motors and Toyota can attest that he has made it more expensive for them to sever their relationships with American workers.