A new Wisconsin ad from a super PAC supporting former Pennsylvania senator Rick Santorum goes negative on former Massachusetts governor Mitt Romney.

A similar spot aired by the Red, White & Blue Fund last week was half positive and half negative; this ad is all negative.

“What kind of president would Mitt Romney be? Just look at his record as governor,” the narrator says, pointing to taxes, slow job growth and of course the health-care law that Romney signed. He concludes: “We just can’t trust Mitt Romney.”

"Rick Santorum and his allies are getting more and more desperate as everyone else realizes he has no path to winning the nomination,” said Romney spokesman Andrea Saul in response to the ad.

A new pro-Romney ad is also out today in Wisconsin; with the primary one week away, the negative ad wars are heating up.