The campaign said in a court filing that it won't go forward with its initiative if U.S. District Judge Michael McShane overturns the ban quickly. Otherwise, the sponsors said, they would press ahead with the campaign - at great time and expense.
McShane has scheduled oral arguments for April 23 on two consolidated lawsuits challenging the gay marriage prohibition.
The campaign must submit 116,284 valid signatures by July 3 to make the November ballot, and organizers say they have more than enough names.
If it qualifies, the initiative must appear on the ballot, even if a court ruling makes it unnecessary.
"In other words, after signatures are submitted, the campaign loses the ability to withdraw the initiative and will have to pursue the campaign no matter what the court decides," campaign manager Mike Marshall said in the court filing.
Also Tuesday, a coalition of 36 Oregon employers, including Nike Inc. and Intel Corp., filed a "friend of the court" legal brief in support of striking down the ban.
The employers say Oregon's marriage exclusion is discriminatory and makes it more difficult to recruit and hire talent.
"Those individuals have choices: they can choose to work in Oregon, which does not permit or recognize same-sex marriages, or they can choose to work in any one of the 17 other states (a list that continues to grow) that permit and recognize such marriages," the document states.
Frank Schubert, political director for the National Organization for Marriage, which does not support gay marriage, disagreed with the argument presented by the employers.
"The top-performing states in the country in terms of the economy are all states that have marriage amendments on the books," he said. "The arguments that these businesses are making are empty to begin with."
In 2004, voters voted to amend the Oregon Constitution to define marriage as a union between one man and one woman. It passed with 57 percent of the vote.
Last fall, Portland attorneys Lake Perriguey and Lea Ann Easton filed a lawsuit challenging the ban on behalf of two women in a relationship for more than 30 years. Two months later, the American Civil Liberties Union and lawyers from two firms went to court on behalf of a lesbian couple and a gay couple.
The lawsuits, which McShane consolidated in January, contend that the state ban relegates same-sex couples to second-class status and deprives them and their children of the dignity and legal protections given to other families. Similar arguments have been made in lawsuits filed across the country.
Oregon Attorney General Ellen Rosenblum announced in February she won't defend the ban, saying it violates the federal constitutional rights of homosexual couples. Moreover, she said Oregon is ready to implement gay marriages if the judge overturns the ban.
Schubert criticized Rosenblum's decision.
"The people of Oregon are entitled to a defense of the laws they've duly enacted," he said. "They're not looking for the attorney general or a group of businesses to substitute their judgment for the judgment that the people lawfully made in passing the marriage amendment."