A little understood, often secretive religious minority in California is having a huge impact on gay marriage in the State. Members of The Church of Jesus Christ of Latter-Day Saints (the Mormons) have contributed between 35-and-40% of the money raised to support Proposition 8 – the constitutional amendment that seeks to ban gay marriage in the State.

Since June, Mormon members have contributed more than a third of the $15.4 million raised by ProtectMarriage.com – Yes on 8, the primary backer of the gay marriage ban, Frank Schubert the group's campaign manager told the Wall Street Journal.

Top Mormon leaders, known as the First Presidency, sent out a letter in June to be read at all California congregations asking members to “do all you can” to support the gay marriage ban.

“The church's teachings and position on this moral issue are unequivocal. Marriage between a man and a woman is ordained by God,” Mormon leaders said. The leaders also urged members to donate their “means and time” in support of the gay marriage ban.

Mormons make up only about two percent of California's population.

The California Supreme Court ruled in May that gay couples have the constitutional right to marry, overturning a 2000 voter-approved gay marriage ban. And on June 15th, the State started offering gender neutral marriage licenses. Since then several thousand gay couples have married.

But Proposition 8 aims to constitutionally forbid gay marriage and would invalidate the thousands of gay marriages that have already taken place.

Similar anti-gay initiatives will greet voters in Florida and Arizona this fall, but religious leaders, particularly evangelical Christians, see California as a crucial battleground. California is the nation's most populous state and holds a high degree of influence over the rest of the country.

Mormon leaders say gay marriage is incompatible with Mormon theology. According to church doctrine, Mormons must be married to achieve “exaltation” – the ultimate state in the afterlife – where they retain their gender and give birth to spirit children.

“This all explains the Mormon difficulty with homosexuality,” said Terryl Givens, a professor of literature and religion at the University of Richmond.

Mormons believe homosexuality is a moral issue. While the 13-million member church has issued a statement saying that being gay is not a sin, non-celibate gays and lesbians face possible excommunication if exposed.

Bruce Bastian is a former Mormon and graduate from Mormon supported Brigham Young University. After the Mormon Church's call for support on Proposition 8, openly gay Bastian donated $1 million of his own money to fight the proposed gay marriage ban.

Bastian, the co-founder of Wordperfect Corporation, has “always been quiet about his [GLBT] giving,” Michael Marriott, Executive Director of the B.W. Bastian Foundation, told On Top Magazine.

That certainly has not been the case with his recent donation in defense of gay marriage rights in California. Marriott says that's because the Mormon Church has been so outspoken on the issue.

“That made him really mad,” Marriott said.

Several years after coming out, Bastian left the church over various church doctrines opposing gays and lesbians. Now, with his four children grown, Bastian has become increasingly vocal in his support for gay and lesbian issues.

In a rare interview with the local Salt Lake City ABC affiliate, Bastian was asked if he believed the Mormon Church should change its stance against gays and lesbians. “I don't think anything I say or do will ever change that. It's my opinion and they are where they are because that's what they believe. But, yeah, I personally believe it's wrong,” Bastian responded.