From Clifford Thies:

The Michigan re-districting mostly benefits incumbent Republican Congressman Tim Wahlberg, who was elected in 2010 with 50 to 45, with 5 points going to third-party candidates (CD - 3). Wahlberg is a social conservative with a libertarian streak on taxes.

The legislature wanted #1 to force the loss of one seat unto the Democrats, and #2 shore up the most vulnerable Republicans, of which Wahlberg was first on the list and Benishek was second.

In 2010, freshman Republican Rep. Justin Amash won 60 to 38 percent, which was a pretty strong margin in an open race (CD - 4). However, he has lost some strong Republican areas and picked up some mixed areas.

There will be four potentially competitive Congressional races in Michigan in 2012: Wahlberg, Benishek, Amash and the district formed by the merging of two Democrat districts. With the state being a purple to feint blue state and a potentially exciting Senate race, all four of these Congressional races will be in play, at least initially.

Image - Current map