"It's just a night and day difference," Hovde said of his subsidies compared to those given to the energy companies.

Hovde and Neumann are battling to be the candidate of choice for conservatives unhappy with former Wisconsin Gov. Tommy Thompson (R), who is also running. The fiscally conservative Club for Growth is backing Neumann with attack ads against both of his main opponents, and this revelation could prove to be ad fodder in the future.