Romney was expected to win at least 12 Michigan GOP delegates, according to CNN estimates.

CNN: Romney's Michigan win shakes up GOP race

But Obama won more states, 13, and leads Clinton in pledged delegates, according to CNN calculations.

CNN: Analysis: McCain clear leader; split decision may help Obama

The battle in the Democratic Party has a long way to go, partly because its system awards each candidates a share of the delegates to the nominating convention according to their share of the vote in each primary.

BBC: NEWS | Americas | Win fires up Obama supporters' belief