Republican U.S. Senate candidate Kurt Bills is going on the air with an ad that accuses Democratic U.S. Sen. Amy Klobuchar of mishandling a case involving a former contributor.

Bills' first television advertisement says that Klobuchar 'refused' to prosecute convicted Ponzi schemer Tom Petters in her time as Hennepin County Attorney and suggests it was in exchange for campaign cash.

Klobuchar has dismissed the charges as completely inaccurate. Her campaign spokesman and an official from the Hennepin County Attorney's office say she was never presented with any prosecutorial evidence against Petters while she held that office.

"Bills's ad is absolutely untrue and the people of Minnesota deserve better than last-minute and desperate attacks based on inaccurate allegations from a convicted felon. He is flat-out wrong on the facts," her spokesman Linden Zakula said.

Petters and his associates, before they got into trouble with the law, gave significant donations to Democrats and Republicans alike. When Petters legal troubles erupted, Klobuchar shed the donations, along with then-Republican Gov. Tim Pawlenty and then-U.S. Sen. Norm Coleman.

Bills campaign spokesman David Strom said Wednesday that their "media buyer is supposed to be getting a spot for the Vikings game tomorrow." He would not say whether the campaign would use the other television spots they had put on order. Asked questions about the ad, Strom declined to answer, saying in an email: "Happy to talk about the issues. The fiscal cliff. Klobuchar's record. Plans to reduce the deficit. Those are the things we want to talk about."

On Thursday, Bills campaign manager Mike Osskopp refused to provide a transcript or back-up material for the ad, as is standard practice, or say whether it would air more than once. Osskopp also did not answer whether the ad was in keeping with Bills stated desire to talk about fiscal issues. He said only, "Ill be glad to answer all of these questions when I read where you asked Amy the question we thought she should answer in our release of yesterday."

Update: In a fundraising plea late Thursday, Bills confirmed to potential supporters that the ad would run during the Vikings game.

The average of all polls of the Senate race show Klobuchar with a nearly 26 percentage point lead over Bills.