The Republican primary in Michigan was won by native son Mitt Romney, after a closely-fought battle with John McCain.
Hillary Clinton won the Democratic primary, although the result is of little more than symbolic value, because - owing to a row about scheduling - national party bosses are refusing to give any delegates from Michigan a seat at the party's national convention.
None of the Democratic candidates campaigned in the state, and the two other frontrunners for the Democratic nomination withdrew their names from the ballot - supporters of Barack Obama and John Edwards had the option of voting for "uncommitted".
The "uncommitted" option came in second place, albeit a long way behind Mrs Clinton.
The Republican party cut Michigan's quota of delegates by half.
Michigan used to be America's industrial powerhouse, but it now suffers from one of the worst unemployment rates in the country, so voters here listened closely to candidates - like Mr Romney - who promised to make job-growth a priority.