SAN FRANCISCO (AP) – Despite their state’s history of promoting gay rights, Californians have been split on the subject of same-sex marriage – a contrast that’s expected to become even more pronounced because of two overlapping voter initiatives.

Fearing that courts eventually will support the rights of same-sex couples to marry, opponents want voters to amend the state constitution to allow only heterosexual unions.

However, a rift among conservatives has led competing groups to promote two different bans and snipe at each other over which is best. Both petitions would do away with rights associated with domestic partnerships as well as same-sex unions.

Conservatives worry the infighting could doom the initiatives, while gay-rights advocates say voters are not likely to discard established domestic partnership rights.

“There is obviously a rift in the family over which of the proposed amendments best protects marriage and protects the rights and benefits of marriage,” said Benjamin Lopez, a lobbyist for the Traditional Values Coalition who tried to unite the competing groups behind one measure earlier this year. “The situation right now is delicate.”

Voters agreed five years ago in a ballot initiative, Proposition 22, that marriage should be only between a man and a woman, but courts said the law violated gay and lesbian couples’ civil rights.

Last week, the California Legislature became the nation’s first legislative body to approve a bill allowing same-sex marriages, although Gov. Arnold Schwarzenegger said he would veto it.

In the ballot initiatives, a group called Vote Yes Marriage favors a detailed, multi-paragraph amendment rescinding the marriage-like rights lawmakers granted domestic partners over the last five years while defining marriage as a union between a man and a woman.

The other group, Protect Marriage, does it in one sentence: “A marriage between a man and a woman is the only legal union that shall be valid or recognized in this state.”

The sponsors have until January to gather 598,105 signatures to put the amendments on next June’s ballot.

Andrew Pugno, legal adviser to Protect Marriage, said that group wants to keep the wording simple as a strategic move.

Backers of the longer Vote Yes Marriage version say that while the Protect Marriage initiative might keep the courts and the Legislature from bestowing marriage licenses on same-sex couples, it would not necessarily do away with domestic partnerships.

Thirteen states already have constitutional bans on same-sex marriage. Others are expected to be on ballots next year in Alabama, Indiana, Wisconsin, South Carolina, Colorado, Arizona, Florida, Virginia, South Dakota and Tennessee. Voters in Texas will decide on an amendment outlawing same-sex marriage this year.

Although Proposition 22 passed with 61 percent of the vote five years ago, a recent poll by the Public Policy Institute of California found that voters are evenly divided on whether gays and lesbians should be allowed to marry. Other polls have found a majority think same-sex couples deserve at least domestic partner rights.

Gay rights advocates said that by attempting to void California’s domestic partner laws as well as ban same-sex marriage, both proposals might be spelling their defeat. But they nevertheless are bracing for the likelihood that at least one will make the June ballot and the possibility that the second would be put before voters the following November.

“Ultimately, it wouldn’t surprise me if this is a way for two different groups to raise as much money as possible and then join forces,” said Geoffrey Kors, executive director of the lobbying group Equality California. “We are suspicious of their motivation because we know they are motivated by wanting to take away the rights of our families.”