Michigan's decision to move its primary to January 15, 2008—a decision signed into law yesterday by Democratic Governor Jennifer Granholm—is sure to have a domino effect on the primary calendar, perhaps moving Iowa's caucuses up to December 2007.
New Hampshire was slated to be the nation's first primary on January 22nd (though South Carolina had already planned to hold its Republican primary on January 19th). New Hampshire will undoubtedly move its primary date up in the month as its "first in the nation" status is actually written into state law.
Republican and Democratic National Party rules have sanctions against states that hold their primaries earlier than prescribed by the party (this election season, February 5th is the cut-off point). After Florida moved its primary up to January 29th, proposed sanctions include having the state lose up to half of its delegates.
The decision by states such as Florida and Michigan appear to indicate they believe having half the delegates in an early contest that means something is more important than having all the delegates count in a primary which means little later in the election season.
Iowa's Governor Chet Culver has assured that his state will hold the nation's first presidential contest—which could mean caucuses in December 2007. That would be several weeks early than the Iowa caucuses held in 2004 (January 19th), 2000 (January 24th), and 1996 (February 12th).
Influential smaller states like Iowa and New Hampshire have not surprisingly been resistant to the recent call by some to have a 'national primary day.'