North Carolina voters have approved a constitutional amendment defining marriage solely as a union between a man and a woman, making it the 30th state to adopt such a ban.

With 35 percent of precincts reporting Tuesday, unofficial returns showed the amendment passing with about 58 percent of the vote to 42 percent against.

In the days before the vote, members of President Barack Obama's cabinet expressed support for gay marriage and former President Bill Clinton recorded phone messages urging voters to reject the amendment.

Meanwhile, supporters ran their own ad campaigns and church leaders urged Sunday congregations to vote for the amendment. The Rev. Billy Graham was featured in full-page newspaper ads supporting the amendment.