Half the voters in the city are disenfranchised because they can’t vote in party primaries, Mayor Bloomberg claimed yesterday as he again pushed the cause of nonpartisan voting.

Whoever wins the Democratic mayoral primary in September is almost certain to capture November’s general election, he said.

The mayor conceded that there are exceptions, such as when there’s a “Bloomberg [who can] spend a lot of money” or a Rudy Giuliani. Between them, those “exceptions” won five of the last five elections.