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Gov. Scott Walker's campaign has transferred another $100,000 to the defense fund used to pay his pricey criminal defense lawyers in the lengthy John Doe investigation into activities during Walker's time as county executive.

Newly filed campaign reports show Walker's campaign transferred $70,000 to the Scott Walker Trust on May 3 and another $30,000 on May 17.

That bring the total the first-term governor has put in the defense fund to $160,000 in the past six weeks.

State law requires that the campaign get prior approval from donors before shifting their money to a legal-defense fund. Walker's campaign has declined to identify the contributors who OK'd the transfers.

Walker has said repeatedly that he and his campaign are cooperating with the investigation, which has led to charges against three of Walker's county aides, one former county appointee and a major campaign contributor. The two-year probe is led by Milwaukee County District Attorney John Chisholm.

Earlier this week, No Quarter reported that officials are looking at an email exchange between Walker and a longtime campaign aide over a 2010 real estate deal. Sources say that the emails were written in late June 2010 - a month later than earlier indicated - shortly before the project went out to bid.

Walker is represented in the case by Milwaukee lawyer Michael Steinle and John Gallo, a Chicago attorney and former federal prosecutor.

Ciara Matthews, spokeswoman for the Walker campaign, said she had no comment on the transfers.

The spokesman for Milwaukee Mayor Tom Barrett, Walker's foe in the recall election, repeated the point that Walker is the only governor in the U.S. with a defense fund.

"If Walker really had nothing to hide, he could have saved himself a lot of money in legal bills by just releasing the emails to the public," said Barrett aide Phil Walzak.

In addition, Walker's campaign is represented by former U.S. Attorney Steve Biskupic of Michael Best & Friedrich since November 2010. Records show the campaign has paid Michael Best a little more than $160,000 for "compliance" issues.