UPDATE, Friday, June 20: Gov. Walker dismisses the allegations detailed below and in a newer article as categorically false. 

Prosecutors in newly released court documents allege that Wisconsin Gov. Scott Walker (R) was at the center of a scheme to violate campaign law by improperly coordinating campaign activities with outside groups.

The documents, released Thursday and part of an ongoing suit, focus on one individual in particular: R.J. Johnson, a Walker aide who prosecutors say directed activities of both Friends of Scott Walker, the governor’s campaign committee, and Wisconsin Club for Growth, a tax-exempt “social welfare” group, during the 2011 and 2012 Senate and gubernatorial recall elections in that state. Prosecutors argue that Johnson used that latter group to fund and guide the activities of several other 501(c)4 organizations, the IRS designation for such nonprofit “social welfare” groups, and that he acted as a “hub for the coordinated activities” of the groups.

(Read more: Gov. Scott Walker dismisses allegations of campaign law violations)

Under Wisconsin law, some forms of coordination between outside groups and a candidate’s personal campaign committee are allowed but are subject to disclosure requirements, according to the filing. Not only were such contributions not disclosed, the prosecutors argue, but banned and above-limit contributions were also made and accepted. The coordination, they allege, “resulted in either prohibited and illegal in-kind or direct contributions.” Defendants argue their actions were legal and allowed under state law.

Prosecutors say Johnson was also coordinating with the Republican State Leadership Committee, the national organization that seeks to elect Republicans at the state level, at least during the 2011 state Senate recall elections. The documents cite a May 4, 2011, e-mail from Walker to political strategist Karl Rove, in which Walker allegedly praises Johnson for his work on the recall elections.

“Bottom-line: R.J. helps keep in place a team that is wildly successful in Wisconsin,” Walker allegedly wrote. “We are running 9 recall elections and it will be like running 9 Congressional markets in every market in the state (and Twin Cities.)”

In notes to Walker that August, Johnson allegedly said that Wisconsin Club for Growth’s efforts were run by himself “and Deborah Jordahl, who coordinated spending through 12 different groups,” according to the filing.

The case involves a two-year-old state investigation into whether Walker’s campaign illegally coordinated with independent conservative groups that poured millions of dollars into Wisconsin to influence the 2012 recall election. The Club for Growth filed a suit to halt the investigation, calling it a violation of free-speech rights. A federal judge agreed, and the case is now pending appeal.

It remains to be seen whether the state prosecutors will prevail. But at a federal level, investigations into illegal coordination between official campaigns and outside groups are exceedingly rare.

Walker’s office referred questions to Friends of Scott Walker. A spokeswoman from that group said, “The Friends of Scott Walker campaign are not party to the federal suit and have no control over any documents in that suit. Two judges have rejected the characterizations disclosed in those documents.”

“This is a shocking development,” Mike Tate, the Democratic Party chair in Wisconsin said. You have a Republican prosecutor saying Scott Walker is at the center of a criminal scheme. You’ve got communication between Scott Walker and Karl Rove dictating activity that by all appearances is in violation of Wisconsin law. We’re not New Jersey, we’re not Illinois. We don’t send our governors to jail. This is a shocking development.”

Dan Balz and Matea Gold contributed.