Santorum ad hits Mitt's 'mud'

Per Playbook, Rick Santorum is going up in Michigan with this ad casting Mitt Romney as a machine gun-wielding political mudslinger, whose "negative attack machine" is "firing his mud at Rick Santorum."

A Santorum aide told my colleague Mike Allen that the ad would be in wide rotation in Michigan. Santorum had reserved less than $50,000 in air time in the state as of yesterday, so we'll have to see what kind of new money Santorum throws down and how much this is a play for free media with a stylistically clever ad.

Amazingly enough, this is the first time this primary season that one of Romney's opponents has had a response ad teed up to go as soon as the Romney/Restore Our Future hits start.