An ongoing John Doe investigation into possible illegal activity by aides to Wisconsin Gov. Scott Walker (R) expanded when Walker's spokesperson, Cullen Werwie, was given prosecutorial immunity. Speculation as to the reasons for the immunity, which authorities haven't revealed, don't signal good news for Walker:

What about the possibility that Milwaukee County resources (or man hours) were used for the benefit of Walker’s gubernatorial campaign?

Could there have been “pay to play” going on within the campaign?

So what could Cullen Werwie have knowledge of? Were there more widespread campaign finance violations beyond those that have already been exposed and prosecuted?

During the 2010 Republican Lt. Governor race, Werwie worked for the campaign of former Republican State Rep. Brett Davis. After Davis was defeated in the September 2010 Republican Lt. Governor primary, Werwie went to work as the traveling press person for Scott Walker’s gubernatorial campaign. In that role, Werwie would have traveled everywhere Scott Walker went, working in close proximity to Walker, no doubt leaving Werwie privy to most – if not all – of Scott Walker’s communications while on the campaign trail.

Despite conservative pundits' claims that the investigation is a witch-hunt, Milwaukee County District Attorney John Chisholm says the investigation is ongoing and it has already produced one conviction and numerous charges against Walker aides.

Among the charges so far:

Due to the highly secret nature of John Doe investigations, few solid facts are publicly known. But what is known indicates that this is a very large investigation, which has expanded to include many people and many possible problems for Walker and his attempt to remain in office.

In May 2010, it was found that one of Walker's county executive staff members, Darlene Wink, was leaving political comments on JSOnline.com and other blogs to promote Walker and his gubernatorial bid while at work. When this information was discovered, she immediately resigned from her taxpayer-funded county post. Since then, investigators have confiscated her work computer and have executed a search warrant of her home.

The revelation of Wink's activities led Milwaukee County Supervisor John Weishan to contact the district attorney's office, inquiring about this as well as an obstruction in an open-records request he had filed with the Walker administration.

At about the same time, Walker took his annual Harley-Davidson ride around the state, purportedly to promote tourism for Milwaukee County. The Democratic Party of Wisconsin sent people to follow Walker and his entourage. During this bike ride, the Democrats shot footage of Tim Russell, then Walker's director of housing and a longtime campaign worker and close friend, traveling with Walker and—as the Democratic Party of Wisconsin alleged—performing campaign-related activities, even though he was traveling as a county employee.

In August 2010, Milwaukee County sheriff's deputies executed a search warrant on Russell's office, confiscating his computer; witnesses say his BlackBerry phone and boxes of documents were also seized.

News regarding Walkergate became scarce for more than a year, but exploded in September 2011, when the home of Walker's trusted aide and top staffer in Milwaukee County, Cynthia Archer, was searched by FBI agents and Dane County sheriff's deputies. The agents removed boxes of items from her home and took the hard drive from a computer that she had just sold to a neighbor a few weeks earlier. After Walker was elected governor, Archer took a top position at the state Department of Administration and, later, the Department of Children and Families.

Just prior to this, Tom Nardelli, who was Walker's chief of staff in Milwaukee County and like Archer had also followed Walker to the state, suddenly resigned from his position at the state Division of Environmental and Regulatory Services.

Another departure, which wasn't revealed until the fall, is that of John Hiller, who suddenly left his position as Walker's campaign treasurer, a job he's held for 18 years.

In the same month, it was learned that several people were granted immunity in the investigation. One of the people granted immunity was Rose Ann Dieck, a ranking member of the Republican Party of Milwaukee County and an acquaintance of Wink's.

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William E. Gardner, president and CEO of Wisconsin & Southern Railroad, pleaded guilty to making illegal contributions, in the amount of $53,800, to Walker's campaign and others. Gardner used company money, laundered through employees and family members, to make these contributions. Gardner ultimately had to plead guilty to two felonies and pay $166,900 in fines.

Also showing that the investigation has taken on different turns is the recent development that Milwaukee-based commercial real estate mogul and former head of the Commercial Association of Realtors-Wisconsin, Andrew P. Jensen Jr., was incarcerated for refusing to cooperate with the investigation. Prosecutors had wanted to offer Jensen immunity, but Jensen would only take the offer if he could keep that information from being made public. In a recent interview, Walker admitted to having met with Jensen on occasion, even though he has tried to downplay these meetings.

These developments have given fuel to allegations leveled by Walker opponents that Walker and his staff have regularly done pay-for-play in which Walker would use his office to reward campaign donors with contracts, government loans and grants and tax breaks, among other political favors. Supporting these accusations, opponents have cited Walker giving contracts to Wackenhut and to Edward Aprahamian—both have donated to Walker's campaign and had received millions of dollars in contracts with Milwaukee County while he was county executive.

The questions continue. In December, five Assembly Democrats asked federal regulators to delay the sale of Wisconsin & Southern Railroad to a Kansas-based company, questioning whether it's "political payback" for illegal campaign contributions to the governor.