The Club for Growth is on the air in Idaho slamming Rep. Mike SimpsonMIchael (Mike) Keith SimpsonHouse retirement sets off scramble for coveted chairmanship The Hill's 12:30 Report Even some conservatives seem open to return to earmarks MORE (R) for voting for the Wall Street bailout in 2008 and accusing him of being "too liberal."

"The facts about Mike Simpson: He voted for the taxpayer bailout of Wall Street, voted to increase the national debt by trillions without any spending cuts," the ad's narrator says. "Simpson teamed up with Democrats to support a bigger Obama stimulus bill and spend millions on a park in Nancy Pelosi's district in San Francisco. Mike Simpson: just too liberal."

The big-spending group has made Simpson, who's facing attorney Bryan Smith (R) in one of the most closely watched GOP primaries in the country, a top target this cycle. Simpson is the only incumbent House member the Club has endorsed against at this point.

The Club says the ad is running on broadcast and cable, though they wouldn't disclose the size of the buy.