"They are very interested in Mark and these groups," a source familiar with the probe told the newspaper. "It is not my sense, right now, that Cain is a target."
Block told TPM back in January that the Cain campaign's investigation into the matter would be wrapping "soon" but has never disclosed the results. He's now serving as treasurer of Cain's super PAC, Cain Connections.
As the Journal-Sentinel explains, the groups appeared to have run into conflicts with several election laws:
Expenses totaling nearly $40,000 are listed in Prosperity USA's internal documents as "due from FOH," a reference to Friends of Herman Cain, the name of his campaign committee.
A number of election law experts have said these payments for campaign events appeared to cross the line.
Prosperity USA also borrowed as much as $150,000 from two unnamed individuals and then gave the bulk of those funds to the Congress of Racial Equality , a conservative civil rights group, in January 2011. Shortly after that payment was made, Cain - who had just entered the presidential race - was a featured speaker at the group's annual Martin Luther King Jr. Holiday Celebration dinner.
Sources said the loans, which don't appear to have been repaid, were obtained under questionable circumstances.
In addition, it does not appear that either organization was granted tax-exempt status, even though contributors were told they could write off their donations. Both groups received substantial support from major conservatives in the state.
The watchdog group Citizens for Responsibility and Ethics in Washington (CREW) filed a complaint with the Federal Election Commission about the use of funds, but the status of that investigation is unclear. The FEC has, however, written letters to the Cain campaign about records that show they exceeded federal limits, took contributions from corporations and made errors about Cain's personal loans to the campaigns, as the Journal-Sentinel reports.