The North Carolina legislature approved a ballot question this week that seeks to amend the state constitution to ban marriage of same-sex couples. The language of the proposed amendment—which could also ban civil unions and domestic partnerships—would make the measure “among the most restrictive in the country,” according to prominent LGBT advocacy groups.

North Carolina already bans marriage of same-sex couples by statute, but supporters of the ballot measure say a constitutional amendment is needed so that the courts cannot overturn the ban.

The House passed the bill 75-42 on Monday, September 12, with ten House Democrats joining 65 Republicans to give the measure three more than the 72 needed for passage.

The party-line Senate vote came a day later, with 30 Republicans giving it the minimum needed for passage, versus 16 Democrats.

The proposed amendment will now appear on the May 2012 primary ballot, not on the November 2012 ballot as sought in an earlier version of the bill.

House Speaker Thom Tillis (R-Mecklenburg) told a press conference that the date change was made to “remove politics” from the issue. Some Democrats had accused Republicans of using the bill to draw conservative voters to the polls in November.

North Carolina is expected to be a key state for President Barack Obama in next year’s presidential elections. He won it by fewer than 14,000 votes in 2008. North Carolina is hosting the Democratic National Convention in September 2012.

But the major contested primaries in May will be the Republican ones for president and governor, meaning the spring turnout will likely be largely Republican.

Marc Solomon, National Campaign Director of Freedom to Marry, said in a statement that supporters of the bill were “politically scheming” to put the measure “on a low-turnout Republican presidential primary ballot.” He called the move “a sham designed to circumvent the majority of North Carolina voters.”

A poll released September 7 by Public Policy Polling found 55 percent of state voters polled would vote against the amendment, versus 30 percent for it. Among Democrats, the ratio was 63 to 23 percent against it, among independents, 52 to 35 percent, and among Republicans, 47 to 37 percent.

LGBT advocates fear the proposed amendment could also ban domestic partnerships and civil unions. The language states that “marriage between one man and one woman is the only domestic legal union that shall be valid or recognized in this state.”

While 29 states have constitutional bans on marriage for same-sex couples, only 18 also ban other forms of relationship recognition.

But Sarah Warbelow, state legislative director for the Human Rights Campaign, said that, while the language of the North Carolina bill will likely be interpreted to prohibit civil unions and domestic partnerships, courts in the other 18 states “have been all over the map” in how they’ve interpreted the similar language of their bans.

In Michigan, for example, the language has been interpreted so broadly as to prohibit public universities from offering health benefits to the same-sex partners of employees.

But in Ohio, cities may still have domestic partner registries.

In North Carolina, several jurisdictions, including the cities of Asheville, Carrboro, Chapel Hill, and Durham, and the counties of Durham, Orange, and Mecklenburg (the state’s largest), currently offer benefits to the same-sex partners of employees.

Warbelow said the proposed amendment “definitely puts those benefits at risk.”

The North Carolina amendment also states that it “does not prohibit a private party from entering into contracts with another private party” and will not prohibit courts from adjudicating such contracts.

Warbelow said the language was likely included to “assuage the fears” of businesses that they wouldn’t be able to offer benefits to employee’s domestic partners if the amendment passes.

But she said that, even without the contract language, private parties would still be able to enter into contracts under the law, and private businesses would be able to offer domestic partner benefits.

She said that, even in the 18 states with the most restrictive amendments, no private business has been prevented from offering such benefits.

Including the contract language, she said, may also help proponents “confuse the public about what potentially is available to same-sex couples.” Many conservatives, she said, like to suggest that same-sex couples can contract for everything they need, and do not need further relationship recognition—even though that is not true.

Several other states are also currently considering ballot measures related to marriage for same-sex couples.

In Minnesota, the legislature has also approved a ballot question for November 2012 that seeks to ban marriage of same-sex couples under the state constitution.

And in Indiana, a proposed constitutional ban on marriage or other relationship recognition for same-sex couples passed the legislature earlier this year. If it passes again in 2013 or 2014, it will be on the ballot in 2014.

Both states already have statutory bans on marriage for same-sex couples.

In Maine, however, LGBT advocates are taking steps to place a citizen’s initiative on the November 2012 ballot, asking voters to approve a law giving same-sex couples the right to marry. LGBT advocates in California and Oregon are also considering similar measures.

But a similar effort in Colorado was dropped this week by the college student who had launched it. He told Out Front Colorado that he was unable to get sufficient financial support for the initiative. The leading LGBT rights group in the state, One Colorado, had never supported the measure, saying that while they applauded the intention, they were focused on legislative solutions.