Donald Trump’s tenure has been a pleasant surprise compared to expectations, which isn’t saying much. His administration has been as chaotic as predicted, driven by his habit of saying unscripted things. But it also has been productive of a few things: corporate tax reform, curbing regulation, injecting a semi-useful ferment into our foreign policy.

The remainder of his term was always likely to be dominated by the enormous baggage he brought with him—his business and personal history.

What...