Darrow Vanderburgh-Wertz waits in a line outside the Durham County Board of Elections on West Corporation Street, Saturday May 5, 2012, in Durham, N.C. Organizers and volunteers for and against the proposed constitutional amendment to ban gay marriage in North Carolina marshaled their forces Saturday to persuade early voters on their way to polling places and remind others to vote on the measure during Tuesday's primary election. (AP Photo/The Herald-Sun, Bernard Thomas)

RALEIGH, N.C. (AP) - It's decision day for a bid to add a proposed ban on gay marriage to the North Carolina constitution so it's much harder to change in the future.

The state votes Tuesday on a constitutional amendment to define marriage as only between a man and a woman, putting North Carolina at the center of a growing debate between generations and America's major political parties over legalizing same-sex unions.

The fate of the gay-marriage ban in the last Southern state without a constitutional amendment hinges on who shows up to vote.

Amendment opponents are drawing support from Democratic Party candidates, younger voters, urban areas and the NAACP. Supporters of the gay marriage amendment are finding their core support in the GOP, older voters, rural areas and conservative black churches.