State Assembly members are gearing up to vote Tuesday on a controversial constitutional amendment to permanently ban gay marriage and civil unions.

If the amendment, officially termed Assembly Joint Resolution 67, is approved Tuesday, Wisconsin voters will then determine the resolution's fate in a Nov. 7 referendum.

While supporters and opponents alike expect representatives to pass the constitutional amendment onto a statewide referendum, their predictions diverge at the ballot box.

"I think the resolution will be passed [this] week with a very strong bipartisan vote coming out of the Assembly," AJR 67 author Rep. Mark Gundrum, R-New Berlin, said, adding he believes most citizens will vote to preserve the fundamental social institution of marriage as it currently exists.

But according to Action Wisconsin spokesperson Ingrid Ankerson, many citizens do not have an accurate understanding of what the amendment entails.

"We believe that Wisconsin is very fair-minded," she said. "And once they know that this would not only ban marriage but also civil unions, and possibly threaten domestic partnerships, that a majority of Wisconsin citizens will vote against the ban."

AJR 67 aims to permanently define marriage as the union between one man and one woman, but also goes further to ban any "legal status identical or substantially similar to that of marriage," according to the resolution's language.

Civil rights activists point to the measure's second sentence as the clause that has them so worried.

"We don't really know exactly [what] 'substantially similar' is," Ankerson said, adding a referendum approval of the amendment would "open up lots of possibilities," including measures to ban domestic partnerships.

If the courts outlawed such domestic partnerships, she added, health care and other benefits could be threatened.

While Ankerson said the resolution's second sentence dangerously places civil liberties at the whim of judicial discretion, Gundrum maintained the sentence is mandatory to preclude a different kind of judicial activism.

"[W]ithout this [amendment], the Wisconsin Supreme Court will sometime within the next few years … do the same thing the Massachusetts Supreme Court did," Gundrum said. "All it takes is four liberal activists."

As the public awaits Tuesday's Assembly vote, Ankerson said Action Wisconsin has long expected the resolution's legislative passage and will continue to promote the organization's public awareness campaign.

"I think that we will defeat it at the ballot box in November," she said. "We have been working for more than two years to educate people about this. Every day that we talk to people we gain votes against the ban."

If the AJR 67 is approved in November, Wisconsin will become the 20th state to add some sort of amendment to its constitution banning same-sex marriage.