"In 1996, we saw one of the most elaborate money laundering schemes in history," Walker said in the release. "Wisconsin voters have a right to know the source of all the money being poured into the state from Washington, D.C. and beyond."

In the context of today's races, the DLCC's 1996 totals were a drop in the bucket. When Walker was first elected governor in 2010, the total spent by the two campaigns and outside special interest groups was $37.4 million. Outside electioneering groups accounted for $12.1 million of that.

"Back in the late '90s, that was a time when candidates both at the legislative and gubernatorial levels had more control over their campaigns and there was less of this massive outside spending by interest groups and other groups," said Common Cause Wisconsin executive director Jay Heck. "So there was more of a bipartisan consensus among Republicans and Democrats that it wasn't good to have this outside, secret money flowing into Wisconsin."