Voters in New Zealand have begun casting their ballots in a general election that has Prime Minister John Key seeking a third term in office.

Polls indicate Key's center-right National Party is the most popular party, and Key is the front-runner to remain the country's leader Saturday. But that could be in jeopardy if opposition parties gain more than half the parliamentary seats and form a coalition.

Key's closest rival is David Cunliffe, leader of the liberal Labour Party.

The campaign was marked by a scandal after a book was published exposing the National Party's links with a conservative blogger. Justice Minister Judith Collins resigned her portfolios as a result.

A party funded by indicted Internet entrepreneur Kim Dotcom is also contesting the election. Dotcom founded the now-shuttered website Megaupload.