"TV Ad Spending By Special Interest Groups Tops $1 Million in Wisconsin Judicial Election."

According to the Brennan Center, as of March 29th. This means that only 18% of the spending has come from the candidates.

Through Sunday, March 27th, three special interest groups had spent more than $1.14 million on TV... Leading the pack is the liberal Greater Wisconsin Committee, which, beginning March 18th, has spent more than $575,000 on blistering attack ads targeting Justice Prosser.... [T]he conservative groups Wisconsin Club for Growth and Wisconsin Manufacturer & Commerce’s WMC Issues Mobilization Council, Inc. have also poured money into the race on pro-Prosser TV ads. Through Sunday, March 27th, the Club for Growth had spent approximately $415,000, and the WMC Issues Mobilization Council about $150,000. These numbers are expected to rise substantially in the final week before Election Day: According to the Brennan Center, 42 percent of all judicial election TV spending in 2010 occurred in the last week of the election season.

Consider that in this race, the candidates both opted into a public financing scheme that capped them each at $300,000.

UPDATE: The Brennan Center's numbers as of March 31st show 4 special interest groups spending more than $2.16 million. Greater Wisconsin Committee has now spent more than $993,000 on TV ads for Kloppenburg. Three groups supporting Prosser have spent more than $1.16 million.