Kurt Bills' tight campaign budget caused him to wait until the final two weeks of the U.S. Senate race to roll out his first television ad. But it's here now, and it accuses incumbent Democrat Amy Klobuchar of trying to cover up the fraud crimes of businessman Tom Petters.

The allegation is that when Klobuchar was Hennepin County Attorney during the 1990's she chose to ignore evidence against Petters. Klobuchar's campaign says the claim is false. County officials say law enforcement did not present Klobuchar with evidence against Petters, who was later convicted in federal court and is serving a 50 year sentence for running a $3.5 billion Ponzi scheme.

It was the conservative website the Daily Caller that first brought the Petters question into the campaign. This week the site posted a video of Klobuchar responding briefly to a Bills supporter asking her about it.

Fundraising reports and polls show Bills trailing far behind the incumbent. The Bills campaign has been critical of the media, particularly the Star Tribune, and the candidate refused to speak to the newspaper's editorial board.

Here is Bills' television ad: