RALEIGH, N.C. — There is a new push for a constitutional ban on gay marriage in North Carolina.

Thirteen states added constitutional amendments last year. Lawmakers in the Senate introduced a bill Monday to do the same.

The bill also invalidates same-sex civil unions and domestic partnerships. Opponents said a constitutional ban is not necessary because state law already defines marriage as the union of a man and woman.

"If we're going to continue to build the society that we have, I think we need to define the institution of marriage as we've traditionally known it," said Sen. Fred Smith, R-Johnston.

"You're talking about families. You're talking about making it more rigid in the constitution of this state -- limiting our rights, making it specific that we have no rights as couples, as families," said gay rights advocate Kathy Heggemeier.

Although there is a new push, supporters of a ban face an uphill climb in the Senate. Last session, the Democratic leadership blocked it from even coming to a vote in committee. The bill sponsors failed to get enough signatures on a petition to bypass the committtee and just bring it to the Senate floor on its own.

This time, the Democratic leadership is making it even tougher by requiring an even greater number of signatures than before.