The state is the only one in the South without such a ban. North Carolina does have a definition of marriage involving a "male and female person" written into state law.
The Coalition to Protect NC Families, which began its efforts this week, has an uphill fight, The (Raleigh) News & Observer reported Wednesday. Recent polls showed registered voters in the state support the amendment 2-1.
The vote will take place during the primary in May, giving the coalition six months to change voters' minds.
So far, voters in state referendums have rejected gay marriage bans only once, in Arizona. Voters there reversed themselves two years later.
Some organizers see signs of hope in the increasing acceptance of gay marriage, which is now legal in six states and the District of Columbia.
"North Carolina really has an opportunity to be on the right side of history here," said Stuart Campbell, executive director at Equality NC. "There is definitely an opportunity to make a case."