North Dakotans gathered enough signatures to force a November vote on a constitutional amendment banning gay marriage, the Secretary of State said Wednesday.

A petition circulated by the North Dakota Family Alliance (search) had 42,093 legal signatures, considerably more than the 25,688 needed to put the idea on the November ballot, Al Jaeger said.

The amendment would deny legal recognition to same-sex marriages or civil unions, an option considered a legal alternative for gay and lesbian couples who seek the rights normally conferred on married people.

At least nine other states are voting on similar constitutional amendments in November.

Robert Uebel, chairman of Equality North Dakota, which advocates for gay and lesbian rights, said opponents of the measure are trying to raise money for advertising to encourage a "No" vote.

"The numbers aren't there for us. That's no lie, that's just the reality. We know that," he said. But he added, "I think public opinion is shifting very quickly."

The issue has already arisen in North Dakota's campaigns for Congress, where the incumbent Democrats, Sen. Byron Dorgan and Rep. Earl Pomeroy, have spoken against a federal constitutional amendment against gay marriage.

An ad by GOP Senate candidate Mike Liffrig, which began airing this week, briefly depicts two men at the altar preparing to kiss as "Here Comes the Bride" plays in the background. "With Sen. Dorgan now supporting gay marriages ... you can kiss our North Dakota values goodbye. Or we can kiss Dorgan goodbye," an announcer says.

Dorgan has denounced the ad as dishonest, pointing to his vote for a federal law that refuses to recognize same-sex marriages.

Similar amendments are on the ballot in Arkansas, Georgia, Kentucky, Michigan, Mississippi, Montana, Oklahoma, Oregon and Utah.

Petitions in Ohio are still being verified, and in Louisiana, the state Supreme Court is considering whether to allow a Sept. 18 vote on a state marriage amendment.

Last month, Missouri voters approved a marriage amendment, with 71 percent of the voters supporting it.