Democrats have virtually no chance of taking control of the Michigan Senate.  The most they can reasonably hope is to pick up some seats.  They are certain to contest the four competitive open seats (13, 17, 20, 32).  It remains to be seen whether they will recruit strong candidates against Republican incumbents.

All but one of the current state senators are former state representatives, and this pattern has held in the past as well.  Thus we can have a reasonable idea who the likely candidates are in many districts.

I have included election data for the 2010 result in the corresponding (old) senate district, and 2008 McCain number and 2006 average (Governor, AG, SOS) for the new districts pulled from Dave's Redistricting App.  My analyses of how much redistricting changed the districts comes from comparing the old and new districts using these elections.  More data is available from Republican Michigander's district profiles.

Republican Michigander district profiles (see sidebar)

The McCain numbers look terrible for Republicans because he collapsed after publically pulling out of Michigan.  The largest McCain percentage in any Michigan state senate district won by a democrat in the past decade is 46.2% in district 31.
Here is a breakdown of the individual races.

1. [Detroit riverfront, Downriver] Safe democrat.
Democrat: Coleman Young (incumbent)
Republican potential candidates: ?
Analysis: One of five black-majority districts based in Detroit.

2. [NE Detroit, Grosse Pointes] Safe democrat.
Democrat: Bert Johnson (incumbent)
Republican potential candidates: ?
Analysis: One of five black-majority districts based in Detroit.

3. [West-central Detroit, Dearborn, Melvindale] Safe democrat.
Democrat: Morris Hood (incumbent)
Republican potential candidates: ?
Analysis: One of five black-majority districts based in Detroit.

4. [Central Detroit, Lincoln Park, Southgate, Allen Park] Safe democrat.
Democrats: Virgil Smith (incumbent)
Republican potential candidates: ?
Analysis: One of five black-majority districts based in Detroit.

5. [W Detroit, Dearborn Heights, Garden City, Inkster, Redford] Safe democrat.
Incumbent: Tupak Hunter (term limited)
Democrat potential candidates: David Nathan, Phil Cavanagh, David Knezek
Republican potential candidates: ?
Analysis: One of five black-majority districts based in Detroit.

6. [SW Wayne, Westland, Taylor] Safe democrat.
Old SS 2010: 37-55, McCain: 33.8, 2006 R Avg: 44
Democrat: Hoon-Yung Hopgood (incumbent)
Republican potential candidates: ?
Analysis: This district also contains the base of term-limited state senator Glenn Andersen, who mounted a credible primary challenge to Congressman John Conyers in 2012.

7. [Livonia, Canton, Plymouth, Northville, Wayne city] Lean Republican.
Old SS 2010: 52-41-5, McCain: 46.6, 2006 R Avg: 59.2
Republican: Patrick Colbeck (incumbent)
Democrat potential candidates: Dian Slavens, Mark Corriveau
Analysis: This Republican district was improved by dropping the southern tier and adding Livonia.  It moved 2.9/3.6% to the right.  Colbeck was a Tea Party candidate who was elected in 2010.  He is the only current state senator who was not previously a state rep.  Colbeck was a leader advocating for Right to Work and could potentially be a target of the unions.

8. [N/E Macomb] Safe Republican.
Old SS 2010: 66-34, McCain: 49.3, 2006 R Avg: 57.9
Republican: Jack Brandenburg (incumbent)
Democrat potential candidates: Sarah Roberts, Jennifer Haase
Analysis: Brandenburg, one of the more conservative Republicans in the senate, is safe in this conservative district.

9. [Warren, Roseville, Eastpointe, Fraser, S Clinton] Safe democrat.
Old SS 2010: 43-54, McCain: 36.9, 2006 R Avg: 45.9
Democrat: Steven Bieda (incumbent)
Republican potential candidates: ?
Analysis: This union-heavy southern Macomb district added Roseville and south Clinton and dropped St. Clair Shores, moving 2.8/2.1% left.

10. [Sterling Heights, Macomb, N Clinton] Safe Republican.
Old SS 2010: 54-46, McCain: 47, 2006 R Avg: 56.2
Republican: Tory Rocca (incumbent)
Democrat potential candidates: Fred Miller, Marilyn Lane
Analysis: Rocca is a fairly moderate senator representing central Macomb.  He was one of four Republicans to vote against Right to Work.  This district was improved by 4.2/4.1% in redistricting after Rocca picked up the previously dem district in 2010.

11. [Farmington, Southfield, Oak Park, Madison Heights] Safe democrat.
Old SS 2010: 33-67, McCain: 25.5, 2006 R Avg: 36.5
Democrat: Vincent Gregory (incumbent)
Republican potential candidates: ?
Analysis: Gregory is a black democrat representing the dem areas of southern Oakland.

12. [NE Oakland, Pontiac, Bloomfield Twp.] Safe Republican.
Old SS 2010: 61-39, McCain: 45.7, 2006 R Avg: 58.7
Republican: Jim Marleau (incumbent)
Democrat potential candidates: Tim Greimel, Tim Melton
Analysis: This district dropped Rochester Hills and added Bloomfield.

13. [Troy, Rochester, Royal Oak, Birmingham] Lean Republican.
Old SS 2010: 59-41, McCain: 45.8, 2006 R Avg: 59.5
Incumbent: John Pappageorge (term-limited)
Democrat potential candidates: Andy Levin, Jim Townsend
Republican potential candidates: Tom McMillin, Marty Knollenberg, Bob Gosselin
Analysis: Pappageorge barely held this district when it was open in 2006, 49-48.4, but easily won in 2010.  It dropped Madison Heights, and moved 1/1.1% to the right.  McMillin is probably the most conservative current member of the state house.

14. [SW Genesee, NW Oakland, Waterford] Safe Republican.
Old SS 2010: 55-40, McCain: 47.6, 2006 R Avg: 58.5
Republican: David Robertson (incumbent)
Democrat potential candidates: ?
Analysis: Robertson, a strong conservative, picked up the previously dem district in 2010.  It dropped dem areas of Genesee, including Burton and Mt. Morris, moving 5.2/5.9% to the right.

15. [SW Oakland] Safe Republican.
Old SS 2010: 62-38, McCain: 47.6, 2006 R Avg: 59.8
Republican: Mike Kowall (incumbent)
Democrat potential candidates: ?
Analysis: Kowall briefly announced a challenge to Congressman Thad McCotter before dropping out.  McCotter was replaced by Kerry Bentivolio after his implosion.  Kowall's wife is a state rep.

16. [Jackson, Hillsdale, Branch] Safe Republican.
Old SS 2010: 64-36, McCain: 49.9, 2006 R Avg: 61.4
Republican: Bruce Caswell (incumbent)
Democrat potential candidates: Marty Griffin
Analysis: Caswell lost 2/3 of his district, Lenawee and St. Joseph, and added Jackson County.

17. [Monroe, Lenawee] Toss-up.
Old SS 2010: 59-38, McCain: 46.8, 2006 R Avg: 54.4
Incumbent: Randy Richardville (term-limited)
Democrat potential candidates: Dudley Spade, Doug Spade
Republican potential candidates: Dale Zorn, Nancy Jenkins
Analysis: Richardville, the senate majority leader, is termed out.  He won 53-47 in 2006 and 59-38 in 2010.  This district is fairly union-friendly, with the state rep seats it contains repeatedly flipping between parties.  The district added Lenawee and dropped portions of Washtenaw and Jackson, moving 1.2/1% to the right.

18. [Ann Arbor, Ypsilanti] Safe democrat.
Old SS 2010: 34-66, McCain: 24.6, 2006 R Avg: 35.9
Democrat: Rebekah Warren (incumbent)
Republican potential candidates: ?
Analysis: Ann Arbor loves electing left-wing feminist state senators, including Warren, Liz Brater, Alma Wheeler Smith, and Lana Pollack.

19. [Calhoun, Barry, Ionia] Safe Republican.
Old SS 2010: 64-36, McCain: 48.6, 2006 R Avg: 57.5
Republican: Mike Nofs (incumbent)
Democrat potential candidates: Kate Segal
Analysis: Nofs picked up this seat previously held by Mark Schauer 61-34 in a 2009 special election.  It moves right 3/1% by dropping Jackson and adding Barry and Ionia.  Nofs is the most moderate Republican in the state senate, and was one of the four Republican votes against Right to Work.

20. [Kalamazoo County] Toss-up.
Old SS 2010: 58-42, McCain: 39.4, 2006 R Avg: 51.1
Incumbent: Tonya Schuitmaker (likely running in district 26)
Republican potential candidates: Margaret O'Brien, Lorence Wenke
Democrat potential candidates: Sean McCann, John Taylor, Mark Totten
Analysis: Tonya won 58-42% in 2010 over Kalamazoo Mayor Bobby Hopewell.  (The result was 53-48 in 2006.)  Hopewell was a last-minute replacement for State rep. Robert Jones, who died shortly before the election.  Tonya is from Van Buren county.  Due to increases in population, Kalamazoo County became large enough to be its own senate seat, and the portion of Van Buren was lost.  This moved the district to the left by 0.3/0.2%.  Tonya is widely expected to run in the new 26th district.  Kalamazoo County is a battleground, with democrats usually winning the top of the ticket, and Republicans doing better at the bottom.

21. [Berrien, Cass, St. Joseph] Safe Republican.
Old SS 2010: 67-33, McCain: 47.4, 2006 R Avg: 57.4
Republican: John Proos (incumbent)
Democrat potential candidates: ?
Analysis: This district swaps Van Buren for St. Joseph, but remains safe for former Fred Upton staffer Proos.

22. [Livingston, W Washtenaw] Safe Republican.
Old SS 2010: 67-30, McCain: 52, 2006 R Avg: 63.5
Republican: Joe Hune (incumbent)
Democrat potential candidates: ?
Analysis: This is the third most Republican state senate district.  Hune has been rated the most conservative member of the state senate.  He could be a candidate for Congress if Mike Rogers runs for US Senate.

23. [Ingham] Safe democrat.
Old SS 2010: 36-64, McCain: 31.4, 2006 R Avg: 44.8
Incumbent: Gretchen Whitmer (term-limited)
Democrat potential candidates: Curtis Hertel Jr., Joan Bauer, Mark Meadows, Barb Byrum
Republican potential candidates: ?
Analysis: Whitmer is the senate democrat leader.  She is one of the few bright spots on the Michigan dems weak bench.  She has ruled out a race for governor, but not for some other office.

24. [Eaton, Clinton, Shiawassee, NE Ingham] Safe Republican.
Old SS 2010: 66-34, McCain: 46.3, 2006 R Avg: 56.2
Republican: Rick Jones (incumbent)
Democrat potential candidates: ?
Analysis: This district drops Allegan and Barry and adds Clinton, Shiawassee, and NE Ingham, moving 4.2/4.1% left.  It is safe for Jones, but could be competitive if open.

25. [St. Clair, Sanilac, Huron] Safe Republican.
Old SS 2010: 67-33, McCain: 49.1, 2006 R Avg: 60.4
Republican: Phil Pavlov (incumbent)
Democrat potential candidates: John Espinosa, Terry Brown
Analysis: This district traded Lapeer for Sanilac, Huron, and a small part of Macomb.

26. [Van Buren, Allegan, Kentwood] Safe Republican.
(New district) McCain: 50.6, 2006 R Avg: 62.6
Republican: Tonya Schuitmaker (incumbent likely running here), Bob Genetski
Democrat potential candidates: ?
Analysis: This new district replaces one eliminated from Wayne County.  It contains Tonya's home and all of her old state house district, but only about 10% of her current state senate district.  Genetski is a solid conservative state rep. from Allegan, while Tonya is usually conservative and resides in Van Buren.

27. [Flint, central Genesee] Safe democrat.
Old SS 2010: 31-66, McCain: 23.6, 2006 R Avg: 31.6
Incumbent: John Gleason (vacant)
Democrat potential candidates: Jim Ananich, Woodrow Stanley
Republican potential candidates: ?
Analysis: The old district was recently vacated by John Gleason, who was elected Genesee County Clerk.  In the special democrat primary, Jim Ananich beat Woodrow Stanley, and is a shoo-in in the general election.  The new district moves 6.1/6.4% left, consolidating the most democrat parts of Genesee in one district.

28. [N Kent, Walker] Safe Republican.
Old SS 2010: 72-25, McCain: 55.5, 2006 R Avg: 67.6
Incumbent: Mark Jansen (term-limited)
Democrat potential candidates: ?
Republican potential candidates: Tom Hooker, Joanne Voorhees, Peter MacGregor
Analysis: This suburban Grand Rapids district is the second most Republican in Michigan.

29. [Grand Rapids, SE Kent] Lean Republican.
Old SS 2010: 51.8-46.5, McCain: 42.1, 2006 R Avg: 57.2
Republican: Dave Hildenbrand (incumbent)
Democrat potential candidates: Dave LaGrand, Brandon Dillon, Robert Dean
Analysis: Hildenbrand narrowly defeated Dave LaGrand in 2010 in the closest state senate race that year.  The district drops Kentwood and adds several very conservative southwestern townships.  It moved right 2.8/2.3%.  Still, Grand Rapids has moved left, so this race could be close.

30. [Ottawa County] Safe Republican.
Old SS 2010: 76-21, McCain: 61.2, 2006 R Avg: 73.7
Republican: Arlan Meekhof (incumbent)
Democrat potential candidates: ?
Analysis: Ottawa County is consistently the most Republican in Michigan.

31. [Bay, Tuscola, Lapeer] Lean Republican.
Old SS 2010: 59-41, McCain: 46.2, 2006 R Avg: 54.3
Republican: Mike Green (incumbent)
Democrat potential candidates: Jeff Mayes, Charles Brunner
Analysis: Green beat Mayes in 2010, picking up the seat formerly held by democrat Jim Barcia.  The new district drops Huron, Sanilac and Arenac, and adds Lapeer.  It is unchanged by 2008 Pres and moves 0.3% left by 2006 avg, though Lapeer is less prone to large swings than the Thumb counties.  Green is the strongest gun rights advocate in the state senate.  He voted against Right to Work, likely for political reasons in this union-friendly district.

32. [Saginaw, W Genesee] Toss-up.
Old SS 2010: 57-43, McCain: 42.4, 2006 R Avg: 50.7
Incumbent: Roger Khan (term-limited)
Democrat potential candidates: Stacy Erwin Oakes, Andy Coulouris, Garnet Lewis
Republican potential candidates: Ken Horn
Analysis: Khan won a nail-biter 49-48.5 in 2006, and was re-elected more easily in 2010.  This district drops Gratiot and adds Western Genesee, moving to the right 0.9/0.4%.  Horn is a moderate who opposed Right to Work in this union-friendly district.

33. [Montcalm, Isabella, Gratiot, Mecosta, Clare] Safe Republican.
Old SS 2010: 65-32, McCain: 46, 2006 R Avg: 56.4
Republican: Judy Emmons (incumbent)
Democrat potential candidates: Mike Huckleberry
Analysis: Emmons was appointed as Republican nominee in 2010 to replace Brian Calley, who was selected to be Rick Snyder's running mate for Lieutenant Governor after winning the primary.

34. [Muskegon, Newaygo, Oceana] Lean Republican.
Old SS 2010: 58-39, McCain: 39.1, 2006 R Avg: 51.4
Republican: Geoff Hansen (incumbent)
Democrat potential candidates: Mary Valentine, Marcia Hovey-Wright
Analysis: Hansen won a blow-out over Valentine in 2010 in a district that usually has competitive elections.  The district drops Mason for population reasons, moving 0.9/0.7% left.

35. [NC Lower Peninsula] Safe Republican.
Old SS 2010: 63-34, McCain: 39, 2006 R Avg: 58.5
Republican: Darwin Booher (incumbent)
Democrat potential candidates: ?
Analysis: Booher was easily elected in 2010.

36. [NE Lower Peninsula, Midland] Safe Republican.
Old SS 2010: 64-36, McCain: 49.9, 2006 R Avg: 57.4
Republican: John Moolenaar (incumbent)
Democrat potential candidates: Andy Neumann
Analysis: Moolenaar defeated Neumann in 2010.  This district could be competitive if open, but should be safe for an incumbent.  Midland punches above its weight politically, always having a state senator and congressman despite only having 42,000 residents.

37. [NW Lower Peninsula, E Upper Peninsula] Safe Republican.
Old SS 2010: 65-35, McCain: 51, 2006 R Avg: 60.3
Republican: Howard Walker (incumbent)
Democrat potential candidates: Gary McDowell
Analysis: Grand Traverse County anchors this district.

38. [Upper Peninsula excluding Mackinac, Chippewa, Luce] Toss-up.
Old SS 2010: 56-44, McCain: 45.3, 2006 R Avg: 47.2 Romney 50.3
Republican: Tom Casperson (incumbent)
Democrat potential candidates: Michael Lahti, Steven Lindberg
Analysis: Casperson beat Michael Lahti in 2010 to become the first Republican to win the UP state senate district in decades.  The district drops Luce, moving it 0.2/0.1% left.  The UP swings substantially depending on the year and the candidate.  Casperson has voted a fairly moderate line in the state senate, in contrast to his record in the state house.  He opposed Right to Work, likely for political reasons.