MADISON (AP) – A legal challenge to the state’s new constitutional amendment banning same-sex marriage and civil unions is gaining momentum.

The lawsuit cleared a key procedural hurdle on Wednesday, a high-profile Madison lawyer has taken the case and the state’s largest gay rights group is supporting the challenge.

Last year, 59 percent of Wisconsin voters approved the amendment in a statewide referendum that prohibits same-sex couples from getting married and the state from recognizing civil unions.

University of Wisconsin-Oshkosh political science instructor William McConkey filed his legal challenge in July, claiming the amendment violates the equal protection clause of the U.S. Constitution.

Lawyers representing the state had asked Dane County Judge Richard Niess to throw out the lawsuit on the grounds that McConkey suffered no harm and therefore did not have legal standing to sue.

But Niess ruled Wednesday the lawsuit could move forward. He accepted McConkey’s argument that his rights as a voter could have been harmed by the way the question was put to voters.

McConkey, of Baileys Harbor, argued the question violated the state Constitution because it asked two questions at the same time: whether to ban same-sex marriages and whether to ban civil unions.

Niess ruled the people were denied the right to vote on each question.

“I believe there is a demonstrable injury to any voter who is required to vote on a question that is constitutionally defective,” Niess said. “Voting is the very bedrock, the very lifeblood of the democracy we have.”

The ruling means the lawsuit can continue but does not indicate what the final outcome will be.

Fair Wisconsin, the gay rights group that led the opposition to the amendment, called the ruling a victory for civil liberties and fairness. The group said it had warned lawmakers about the defective question before they placed it on the ballot.

“All Wisconsin voters have a right to a procedurally legitimate referendum on a proposal to amend Wisconsin’s Constitution, and all voters are harmed by having a constitutionally defective question placed before them,” said group vice president Michele Perreault. “It’s clear there were two distinct questions on the ballot – and that is not constitutional.”

McConkey described himself as a “Christian, straight, married” father of nine and grandfather of seven when he filed the lawsuit. He is also a motivational speaker and author of the book How Voters Choose.