The part that surprised me was Northern Michigan. The only think I can think of there would be absentee voters which broke heavily against Santorum statewide. I was a little surprised at Jackson and Livingston County as well because of the social conservatives there. Could be the absentees there too.
Most of our state political operatives have second homes up north. I’m sure they make sure someone lives there to vote and it only takes a few votes to move those elections one way or another due to the sparse population.
Some years back I learned that Debbie Stabenow owned the house next door to me but had likely never laid eyes on the place. I asked a realtor who was selling the place about it. She wouldn’t say who owned it but did say that the owner wasn’t making any money so there was probably a political reason for owning it.