Last week, federal prosecutors apparently closed the books on the whole sordid mess that will forever stain Gov. Bob McDonnell’s administration.

“More than 3½ years after learning of an investigation, the final day of vindication has arrived,” McDonnell said after the Justice Department announced last Thursday that it would not continue to pursue criminal charges against the former governor and his wife, Maureen.

Two years ago, McDonnell and his wife were convicted in federal district court on corruption charges after taking more than $177,000 in gifts and loans allegedly in exchange for promoting a company’s dietary supplement. In June, those convictions were vacated by the U.S. Supreme Court and sent back to the appeals court to see if there was enough evidence for a possible retrial.

The basic facts of the case—that Bob and Maureen McDonnell accepted these gifts and loans and they promoted the Anatabloc supplement—don’t appear to b...