A new round of criminal charges is coming soon against at least a couple of Gov. Scott Walker's former county staffers for doing extensive campaign activity while on the taxpayers' dime, sources say.

The charges - which should be filed by District Attorney John Chisholm's office in the next week or two - will be part of the long-running John Doe investigation of Walker's aides and associates during his tenure as Milwaukee County executive.

Already, the probe has led to multiple felony charges against Walker's onetime deputy chief of staff, Tim Russell, and former county veterans official Kevin Kavanaugh. They are accused of taking more than $60,000 in donations intended for Operation Freedom, an annual event at the county zoo for veterans and their families.

Russell's domestic partner, Brian Pierick, was also hit with two felony counts for child enticement.

In an interview last week, Walker said he has not been contacted by investigators for the Democratic district attorney but would be open to sitting down with Milwaukee County prosecutors to discuss the issues they are investigating.

"I certainly would be willing if they asked me to in the future," Walker told the Journal Sentinel's Madison bureau. "Like I said, no matter who it might be about, we'd be more than willing to in the future."

Asked if he has hired his own attorney for advice regarding the John Doe investigation, Walker declined to answer.

"I've not been a subject of this," the first-term Republican governor said. "At some point in the future, if I am, I'll discuss that with you."

His campaign hired Steve Biskupic of Michael Best & Friedrich in late 2010, when officials subpoenaed campaign emails. Last year, Walker's campaign paid Michael Best nearly $110,000 for "compliance issues."

At least eight of his former aides and associates have hired criminal defense lawyers.

A John Doe is a secret probe of a possible criminal matter that allows prosecutors to compel testimony and seize evidence.

The upcoming charges, sources said, will not mark the end of the 20-month criminal investigation.

The next phase, insiders say, is focusing on the role some of Walker's closest associates and county employees had in a real estate deal involving a county agency. The point man on the deal, real estate broker Andrew Jensen, was arrested last month for allegedly failing to cooperate with the investigation. Jensen, who was not charged, is set to meet with prosecutors this week.

Assistant District Attorney Bruce Landgraf declined to discuss any phase of the probe - including whether taxpayers footed the bill for campaign labor.

"I officially have no comment whatsoever," Landgraf said Friday.

Insiders were likening the upcoming charges to an earlier political corruption scandal.

"It's going to be along the lines of the (Steve) Foti and (Scott) Jensen cases from the caucus investigation," said one knowledgeable source.

The comparison is an interesting one because Walker, as a state lawmaker, was untouched by the well-publicized state caucus investigation, which concluded the partisan legislative caucuses were taxpayer-financed campaign machines for their respective parties.

Beginning in 2002, prosecutors charged a number of lawmakers and staffers - both Democrats and Republicans - as part of their investigation into state employees illegally campaigning on taxpayers' time.

Foti, the former Assembly majority leader, pleaded to a misdemeanor in January 2006 for directing an aide to campaign on state time. Jensen, the ex-Assembly speaker, was originally charged with three felony counts of misconduct in office, but he eventually was convicted of a misdemeanor and ethics code violation. Now an adviser to a school choice group, Jensen was required to pay a $5,000 fine and reimburse the state $67,174 for legal fees.

Both Jensen and Foti are Republicans.

Milwaukee County prosecutors had a hand in that investigation, winning a conviction of former Senate Majority Leader Chuck Chvala, who pleaded to two felonies for having a state worker campaign while on state time and for illegally funneling cash into the election fund of a fellow Democrat.

The current case was launched in May 2010 - about a week before one Walker staffer, Darlene Wink, resigned from her county job. She acknowledged to No Quarter that she spent much of the day working on a private laptop posting comments and posts online touting her boss when she was supposed to be doing her job providing help to Milwaukee County constituents. Walker's chief of staff said at the time that "no one in our office had any knowledge" of her activities.

Prosecutors raided Wink's house less than three months later.

It is not clear if the upcoming charges will involve anyone from Walker's successful 2010 gubernatorial campaign.

Chisholm's office subpoenaed Walker's campaign emails on Nov. 1, 2010 - one day before the general election, according to a source familiar with the matter.

In his interview with the Journal Sentinel, the governor emphasized that prosecutors have not asked for his phones, computers or other electronic devices. But he didn't provide a clear answer if the same was true for his staff during his successful 2010 gubernatorial campaign.

He initially said he didn't know about anyone else. Pressed again, he said, "I haven't looked in with anybody else, but not to my knowledge."

Wouldn't his staff tell Walker if the cops showed up and started seizing equipment from his campaign headquarters?

"I answered your question," he said. "I don't know of anything else right now."

Contact Daniel Bice at (414) 224-2135 or dbice@jrn.com. Follow him on Twitter @NoQuarterr.