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Michigan has not represented a threat to the calendar -- at least not to jump any further forward than February 28 -- since the Michigan Republican Party passed a resolution calling on the Republican-controlled state legislature to set a date between the last Tuesday in February and the first Tuesday in March. At the end, Michigan is in the calendar spot it was in since its non-compliant January 15 primary was held in 2008; the fourth Tuesday in February date called for by state law.
That was solidified when the state legislature in September passed a bill keeping the date on February 28 but also "closing" the presidential primary.1 That bill (SB 584) -- including the presidential primary date -- was signed into law by Governor Rick Snyder (R). Michigan, then, officially became non-compliant today. With a pre-March 6 date, Wolverine state Republicans will lose half of their delegation to the Republican National Convention in Tampa.
For a history of the process to change/keep the primary date Michigan follow the Michigan post history. And find an updated 2012 presidential primary calendar here.
1 The primary is not formally closed as in other states. Primary voters are required to sign a sworn statement that they are a member of the party of the ballot they are requesting.