The Michigan Republican Party will decide on Saturday, August 13, whether to use a presidential primary or a caucus to choose delegates to the 2012 national convention. See this story. If the Republican Party decides on a caucus, it is likely the legislature, which reconvenes in September, will eliminate the presidential primary for 2012, since the Democratic Party has already decided to use a caucus in 2012. If the Republican Party chooses a presidential primary for 2012, the legislature will probably pass a bill setting the date that the Republican Party prefers. The article seems to feel that the Republicans will opt for a primary to be held February 28, which would violate national Republican Party rules. Thanks to Thomas Jones for the link.
Michigan has other ballot-qualified parties: Americans Elect, Constitution (called U.S. Taxpayers Party in that state), Green, Libertarian, and Natural Law. However, Michigan election law doesn’t give those parties their own presidential primary.