[A]lthough there is no crime called collusion, in criminal law, working with others toward an unlawful end is known as conspiracy. And conspiracies to defraud the United States under 18 U.S.C. 371 include those that impair, obstruct, or impede lawful government functions such as carrying out a federal election. That is the legal theory that special counsel Robert S. Mueller III has used to charge the Russian defendants. Although this indictment charges only Russians with taking part in that conspiracy, the same charge would potentially apply to any American co-conspirators. [...]

Once an indictment is returned, the grand jury's work on the charged offenses must cease. If the investigation is not yet complete, prosecutors could choose to bring an initial indictment against Russian participants while continuing the grand jury investigation against others.

That procedure could make sense. Friday's indictment sets a dramatic stage for anything that will follow. It provides the most detailed public account to date of the activities that Mueller is charged with investigating, and puts to rest any notion that there is "no there there." It also lets other potential targets know that Mueller's knowledge of Russian interference is extensive, and that the wisest course may be to cooperate rather than to try to obfuscate or obstruct.

Bringing the first major indictment against only Russian individuals is also a brilliant rebuttal to those who argue (without basis ) that Mueller's inquiry may be politically motivated. It allows Mueller to reveal the breadth and seriousness of the misconduct without any distracting political sideshows. Surely the condemnation of the conduct set forth in Friday's indictment will be bipartisan and overwhelming. That will give Mueller's investigation considerable momentum and should provide substantial political insurance against any potential moves to fire the special counsel.

If the investigation into election meddling remains ongoing, then a superseding indictment could later add additional co-conspirators and charges. On that point, it is interesting to note the indictment's allegation that the defendants conspired not only with each other , but also with "others known and unknown to the Grand Jury."