A state or county criminal investigation that begins with abuse of the Donald J. Trump Foundation need not be limited to violations of charity and election law. It can also examine his personal and business tax filings and, in the process, lawfully put his tax returns in the public record.

Mr. Trump reportedly used hundreds of thousands of foundation dollars to settle legal cases and buy portraits of himself that hang at Trump properties, among other egregious examples of self-dealing. Those foundation expenditures were income, and unless Mr. Trump reported that income, he could be prosecuted for criminal tax fraud.

The civil complaint and other documents released by the attorney general’s office show that this case meets the standards for criminal prosecution: repeated misconduct over many years, large sums of money involved and efforts at concealment. A prosecution would also promote the goal of deterrence.