Here’s where things get complicated. State law bars campaigns from coordinating with “independent expenditure” groups that “advocate for the election or defeat” of a candidate. However, the conservative groups targeted in the investigation, such as the Wisconsin Club for Growth, avoided using key terms such as “vote for” or “vote against.” Instead, they spent millions of dollars on ads in which they praised Walker or bashed his opponents.

The effect on the voter is likely the same, but in legal terms, the two messages are completely different; a group that does not “expressly advocate” for the election or defeat of a candidate is not subject to many of the same regulations as others that do. They do not have to disclose their spending or donors to state election officials, for instance.

However, at least two judges cited this distinction in casting doubt on the merits of the investigation. Gregory Peterson, a retired appeals court judge appointed to oversee the investigation, quashed a number of subpoenas sought by prosecutors, ruling that there was not probable cause of illegal activity because the targeted groups, such as the Wisconsin Club for Growth, were “issue advocacy” groups.