Both the Republican and Democratic parties have rules against this. The Republican Party stripped half of Michigan's delegates. The Democratic Party played things a little differently, and it turned into a three-ring circus.

The initial response of the national Democratic party was to tell Michigan not to hold a Democratic primary at all. When it became clear that Michigan intended to hold the election anyway, the party ordered their candidates to withdraw their names from the primary ballot. Edwards, Obama, Biden, and Richardson obliged and withdrew their candicacy. Clinton, Kucinich, Gravel, and Dodd did not withdraw. 

Michigan Governor Jennifer Granholm endorsed Hillary Clinton for President.

On December 1, the Democratic Party decided to strip Michigan of all of its delegates. Although there have been rumors that either or both parties might reinstate the delegates from Michigan, as things stand now the Democrats from Michigan get no votes, and the Republicans get half.

Now, a lawsuit has been filed in U.S. District Court to stop the Democratic primary on the grounds that the party was within its rights to instruct Michigan not to hold a primary since it was in violation of the rules. A court date has not been set yet, but it is likely a ruling will be forthcoming before the primary on January 15.

Where do things stand right now for Michigan's Democrats?

The voter's guide from the Democratic Party of Michigan website states in part,

“7. The Democratic ballot will have 6 choices:

Hillary Clinton

Christopher Dodd

Mike Gravel

Dennis Kucinich

Uncommitted

Write-in

8. A vote for “uncommitted” is a vote to send delegates to the Democratic National Convention who are not committed or pledged to any candidate. Those delegates can vote for any candidate they choose at the Convention.

9. Supporters of Joe Biden, John Edwards, Barack Obama and Bill Richardson are urged to vote “uncommitted” instead of writing in their candidates’ names because write-in votes for those candidates will not be counted under state law. “

So, we have three possible outcomes from this mess:

• The court could disallow the Democratic election altogether.

• The election might go forward, but no votes will count in the national convention.

• Or, the election could go forward, and some or all of the delegates will be restored to the national convention. But then, the ballot is stacked to assure a win for Hillary Clinton. So it won't matter who individuals vote for, the result has been fixed, barring a come-from-behind surge for Dodd, Gravel, or Kucinich.