RALEIGH, N.C. (AP) — People who favor adding a ban against gay marriage to North Carolina's constitution are hoping for a big push from churches statewide.

The group Vote For Marriage NC is urging church leaders to preach a marriage-themed sermon on Sunday and encourage congregants to vote early on Monday. North Carolina's early-voting period runs through next week ahead of primary election day on May 8.

North Carolina already outlaws gay marriage, but adding that ban to the state constitution would make it much harder to change in the future.

Amendment backers also want churches to show a video in favor of rejecting domestic partnerships and defining marriage as only between one man and one woman.

Supporters are largely waging a grass-roots campaign in churches and conservative networks to pass the amendment.