Wisconsin gubernatorial candidates and outside groups have spent more than $8.3 million on broadcast TV ads, with $3 million spent in the last 30 days alone.

The Democratic gubernatorial primary is on May 8, while the general election is still a month away, on June 5. But the race is already the most expensive in state history, with Gov. Scott Walker (R) bringing in more than $13 million in the last three-month reporting period.

According to media tracking by the Campaign Media Analysis Group and analysis by WisPolitics.com, only $208,510 of money spent on TV ads has been for spots positive in tone. More from WisPolitics:

In all, CMAG numbers show the pro-Walker side has far outspent the anti-Walker side on broadcast TV since November -- more than $5.1 million to more than $3.1 million.

But in the past 30 days, the pro-Dem forces have had the edge, $1.6 million to $1.4 million.

Those totals do not include ads run by the MacIver Institute and Americans For Prosperity. That ad buy -- estimated at $2.9 million on broadcast and cable -- did not mention Walker, but bolstered the reforms he pushed through the Legislature last year.

The numbers cover broadcast TV ads run in the top six markets covering Wisconsin -- Duluth, Green Bay, La Crosse, Madison, Milwaukee and Wausau – between Nov. 1 and Wednesday; cable buys aren't included. These buys indicate where the campaigns are focusing their efforts and how they're trying to appeal to potential voters.

Walker's campaign has spent more than $3.6 million since Nov. 1, with almost $1.3 million going into the Milwaukee broadcast market. The Right Direction Wisconsin PAC, which is run by the Republican Governors Association, has spent nearly $1.4 million.

On the Democratic side, Wisconsin for Falk, the super PAC backing former Dane County executive Kathleen Falk, has spent $1.9 million, while Falk herself has spent $180,710. Milwaukee Mayor Tom Barrett, meanwhile, has spent $534,630. The Greater Wisconsin Political Fund, an independent political organization known as a 527, spent $507,280 on negative ads against Walker.