North Carolina lawmakers will return to Raleigh on September 12 to begin debate on a constitutional amendment that would ban gay marriage.

The special session on constitutional amendments will consider whether to send three issues to the ballot box in 2012. Among them is a proposal to define marriage as a heterosexual union.

The legislation was introduced in the Senate in February and in the House in April.

The Senate version explicitly bans other unions in addition to marriage, which might include civil unions and domestic partnerships, but the House version only covers marriage. Gay rights activists worry that the Senate version could outlaw domestic partner benefits currently offered by private sector employers.

According to gay weekly Qnotes, opponents of the ban will rally outside the state capital on Tuesday, September 13.

Alex Miller, interim executive director of Equality North Carolina, the state's largest gay rights group, told the paper that the amendment's passage was “not a foregone conclusion.”

“There is a tremendously well-funded and well-organized effort by groups pushing this amendment to see it passed at all costs, so it is important for constituents to contact their legislators, to have business owners contact representatives and to share individual, personal stories on what kind of real-life impact this amendment would have on people.”

“It is crucially important that everyone understand that this fight is far from over,” Miller added. “When the bill is brought up for a vote it will either pass or fail by one or two votes. I can tell you that ballot campaigns are incredibly expensive and time consuming and almost always fail. We have better things to do for the next 14 months than fight what will be an enormously costly battle that would ultimately be bad for this state.”

Minnesota lawmakers have already approved a plan to place a similar amendment on next year's ballot.

(Related: NC House Speaker Thom Tillis says let's put gay marriage up for a vote.)