The fundamental problem in the Hastert case is simple: what, exactly, is the crime? As presented, the crime consists of a series of structured withdrawals supposedly designed to avoid a reporting duty, about which Hastert misled federal agents when they questioned him. This is not only extraordinarily thin gruel, it is also ripe for abuse. Keep in mind that the prostitution scandal that was manipulated by a Bush-era prosecutor to end the career of Eliot Spitzer was also triggered by similar bank payment reports.

Having bank reporting requirement makes good sense—it makes life tough for drug dealers and money launderers. They can be charged for drug dealing and money laundering. But to make a violation of the reporting requirement itself the crime that is charged? That’s a stretch. Moreover, it points to just the sort of prosecution against which we should be on guard. America’s greatest modern prosecutor, Robert Jackson, reminded prosecutors that they should always be investigating crimes and not people. The latter may be common, but it is inherently an abuse of prosecutorial power. But so far this case looks disturbingly like the search for a crime in the pursuit of Denny Hastert.

The Justice Department’s record in prosecuting politicians in recent years has been a decidedly mixed bag. It embarrassed itself enormously with the prosecutions of the late Alaska Senator Ted Stevens and former Alabama Governor Don Siegelman—and has so far has only owned up to its misconduct in the first case, under strong pressure from a federal judge. On the other hand, its prosecutions of Illinois Governor Rod Blagojevich and Virginia Governor Bob McDonnell reveal prosecutors doing exactly what the public expects of them. The prosecution of former North Carolina Senator and Democratic Presidential candidate John Edwards reflects the more borderline case involving technical failings in campaign funding: the politicians involved richly deserved to have their dealings exposed and to be embarrassed. But prison? That only compounds our existing problem with too many victimless crimes, too many prisoners and too many jails.