MILWAUKEE-Washington lobbyist Tommy Thompson was set to headline a GOP gala today that was organized by a Republican operative who is part of the criminal corruption probe of the Scott Walker campaign.

Roseann Dieck, a longtime Republican activist and officer in the Republican Party of Milwaukee County, was granted immunity from prosecution in the ongoing John Doe corruption probe that has also involved Walker's chief of staff, spokesman, campaign treasurer, former deputy chief of staff and other powerful top aides.

Dieck was listed as the coordinator for the Friday fundraiser at the Italian Community Center in Milwaukee.

"Given the number of Scott Walker Republicans that have been ensnared in the corruption probe against Scott Walker, this year's Republican gala in Milwaukee should come with the promise of immunity from prosecution," Democratic Party of Wisconsin Chair Mike Tate said Friday. "Since Tommy Thompson is a lawyer, maybe he will have good advice for his fellow Republicans as they seek to avoid being put in chains."