There's a lot being said about Santorum taking the lead to some degree in most opinion polls. If Santorum wins Michigan, it will be gigantic from a PR, momentum, and fundraising standpoint. From an actual delegate standpoint, it's more complicated than that.
Michigan loses 50% (30) of the delegates for having the election before Super Tuesday. Part of the reason Michigan moved their primary up is because State Party wanted a primary and not a convention. By law in Michigan, elections are held only four days in a year (in response to MEA and school elections)
You can lose the state, and take more of the districts. From what I can find, delegates are apportioned in this fashion.
Two delegates selected at large proportional based on 15% of the vote. I don't know how that would work with two delegates.
Two delegates each, winner take all per NEW 2012 congressional district. These are the new districts, not the current districts. A map of the new districts are here.
Mitchell Poll - Santorum up 17% in Grand Rapids Media Market, 9% in Non Detroit Media Market, 7% Detroit Media Market.
Detroit News poll - Comment - "Oakland County is an island for him"
MRG Poll - Santorum up 3 over Romney in Lansing media market, Santorum up 45 in the UP, Santorum up 18 in Traverse City Market, 16 in Grand Rapids Market, four in Detroit and Flint media markets. Romney up 8 in Oakland County. Tied in Macomb.
PPP Poll by Area Code:
231 - Santorum up 20. 231 is West and Northwest Michigan from around Muskegon north to Petoskey.
248 - Romney up 14. 248 is Oakland County.
269 - Santorum up 14 over Newt. West and Southwest Michigan from around Hastings to Battle Creek to Kalamazoo to St Joe to New Buffalo.
313 - Santorum up 10. 313 is part of Wayne County. Detroit, Redford, Grosse Pointes, Dearborn.
517 - Paul up 3 over Santorum and Romney. 517 is largely Lansing area, Jackson, Western Livingston County, and Hillsdale.
586 - Santorum up 15 over Newt. (Strongly contradicts PPP) 586 is Macomb County.
616 - Santorum up 13. Grand Rapids, Holland, Ionia.
734 - Santorum up 22. Ann Arbor, Monroe, Ypsi, part of Wayne County (Livonia), small part of Southern Livingston County.
810 - Santorum up 13. Brighton, Flint, Lapeer, Port Huron.
906 - Santorum up 22 over Newt. That is the UP.
989 - Santorum up 20. Saginaw, Bay City. Northern Lower Michigan.
M1-01 - North Michigan. As of now, it looks like Santorum's best district. 906, some 989, and some 231 area codes. It's a very blue collar area outside of parts of the Lake Michigan Coastline. The UP is conservative, but more than anything else despises phonies. McCain won most of this area in 2008. Advantage Santorum
M1-02 - West Michigan Coast, from Holland to Ludington. 616 and 231. Ottawa County is the most republican county in the state. It's going to drive this district. Muskegon County could factor in with crossovers and independents, along with the base. The rest of the district is rural populist. The life issue is BIG here. Advantage Santorum.
MI-03 - Most of Kent County, Ionia and Barry Counties, Calhoun County. 616, 231, 269. Ionia and Barry are rural populist. Grand Rapids suburbs will drive the turnout here. Calhoun County could impact things. Advantage Santorum.
MI-04 - Rural North and Central Michigan. From Lansing's Northern border up to Cadillac and Roscommon. From Big Rapids to the Saginaw suburbs. Mostly 989, maybe some 231. Santorum should do well here.
MI-05 - This is a blue district, but just as important for delegates. Mostly 810 and 989. Genesee County, Western Tuscola County (important for GOP), Saginaw area, all of Bay County, Arenac County and Iosco County. White union crossovers and independents may be the key here in the Flint suburbs, some Saginaw suburbs, and especially Bay County and the Standish/Tawas area. There's a small GOP base area near Fenton (Frankenmuth's now in the 4th).
MI-06 - SW Michigan. 269 area code. The new MI-06 now has ALL of Allegan County which is just as republican as Ottawa County (Southern Allegan is competitive reducing the county percentage). All of the counties have significant GOP populations (Kalamazoo County is dem, but not ALL dem) to impact this district. District went big for McCain last time. Polls are showing Santorum up here, but it's tough for me to call. Upton wins here too.
MI-07 - South Central and Eastern Michigan. 517 and 734. This district no longer has Calhoun County and picks up Monroe County. Monroe is quite populist and often hostile to a Romney type Republican. They usually (not 2010) like John Dingell types of democrats and Randy Richardville types of Republicans. Much of the district is populist independent conservative. Romney's best hope here is a good showing by Ron Paul.
MI-08 - 517, 810, some 734, and 248. The 8th district changed some. It keeps Ingham County and Livingston County, but adds more of Oakland while dropping Shiawassee and Clinton Counties. That MAY help Romney. The question is this. Where in Oakland County, is Romney's strength? Is he leading based on across the board strength, or is it concentrated in the Bloomfields and getting drilled in places like Clarkston. The new 8th covers "North Oakland" is a lot different than what people think of when they think of Oakland County. There isn't a lot of difference between North Oakland and Livingston County when it comes to politics, even though Livingston has a much more conservative reputation. Both of those areas are social conservative, BUT also are fiscally conservative as well. I think the 8th is up for grabs. All candidates have strengths and weaknesses for this district.
MI-9 - This is the new 9th, much like the old 12th. 248 and 586. It's now Macomb County based, while also taking in the white parts of SE Oakland County, as well as Bloomfield Township. This may have been Mitt's old home (or it could be the 11th). The question here is which poll is accurate with Macomb County. This is a blue district, but with a couple of significant GOP populations. Bloomfield Township, parts of Sterling Heights, and parts of St Clair Shoes and Clinton Townships. There's much more GOP vote here in Macomb County. If Mitt gets the GOP votes in Oakland all out and his way, he's going a chance at this. I bet he's up BIG in Bloomfield Township and Southfield Township (Bingham Farms). Edge Romney due to that.
MI-10 - 586, 810, maybe 989. This district is the home of Reagan Democrats. Northern Macomb County, and the thumb. Most of the votes here are in Macomb, but the thumb is also very important. Lapeer is a base county. St Clair is competitive. The rest of the thumb is conservative, but not necessarily Republican. I think Santorum will take the 10th.
MI-11 - 248, some 734. This district is a mix of mostly the old 11th and old 9th. Advantage Romney. It's mostly in Oakland County, along with some western Wayne County suburbs. It drops a lot of the union territory to Dingell or Conyers. This district has Troy, Bloomfield Hills, and Birmingham which gives Romney an advantage. Livonia's tougher to read and is a little more Reagan Democrat. Canton's very tough to read. Plymouth, Novi, and Northville areas are on paper more Romney friendly. I think the South Lyon, Highland, and Milford areas will be a little tougher for him. I'll be shocked in Romney loses here through.
MI-12 - 734, some 313. This district stretches across Southern Wayne County from Dearborn and Downriver to Ann Arbor. I was a little shocked to see Santorum win big in 734 territory according to PPP, but I think a lot of the republican vote here will be from West Dearborn and South Downriver. I think crossovers will decide this district. For whom is the question. Ann Arbor will likely cross over for Ron Paul. Downriver for Santorum (stick it to Romney).
MI-13 - 313, 248. This is a VRA district, but has a small and significant GOP base for a primary of this type. The Grosse Pointes. There's significant GOP minorities in Farmington Hills and West Bloomfield as well. I think Romney takes this district unless enough blacks cross over.
MI-14 - 313, 734. This is also a VRA district, but does into the more populist Western Wayne County suburbs. There's significant (for this district) republican minorities in Redford, Dearborn Heights, Westland, and Garden City. I think Santorum has an advantage there.
If things stand as they do today, I'd pick Santorum to win districts 1-7, 10, and 14. I'd have Romney winning 9, 11, and 13. I'd have the 8th and 12th up for grabs.