I don't really see what Santorum has to do with any of this (other than the BRTD/Keystone Phil circlejerk). Pennsylvania residency requirements are rather relaxed, whereas Louisiana's are quite draconian. If Santorum was in Louisiana, he might not be able to run either.
The Santorum issue and the hypocrisy of most Dems here has plenty to do with this. Breaux had basically nothing to do with Louisiana for a few years now but his residency wasn't an issue for most Dems. Santorum, however, was a punching bag on his residency scandal. I'm just noting the hypocrisy, Sam.