The Trump administration has so far announced 43 equity stakes in firms producing everything from minerals to semiconductors, 36 of which were negotiated without explicit legal authority — and more are yet to come. The administration may be negotiating even more stakes under the radar, since SEC filings for unrelated deals mention the possibility of warrants. Unwinding the administration’s investments would prove legally and politically difficult — but Democrats likely won’t want to, at least not right away. They’re already weighing how to use equity stakes for their own ends, signaling that Trump’s government intervention in the private sector may...