Opponents of a ballot measure to ban gay marriage refused to concede this morning, despite vote totals that show supporters of Proposition 8 with a 400,000-vote advantage.

Kate Kendall, executive director of the National Center for Lesbian Rights, said 3 million to 4 million ballots remain uncounted statewide.

"The fact is depending on the turnout model we are looking at millions of votes yet to be counted," Kendall said. The race is too close to call. People's fundamental rights hang in the balance."

Secretary of State Debra Bowen is expected to issue an estimate of the number of uncounted ballots late today or Thursday. It could take days to process all of them. Proposition 8 supporters declared victory early today, saying their model shows them with an insurmountable lead.

Proposition 8, the most passionately debated and costliest measure on the ballot, was ahead 52 percent to 48 percent with 92 percent of precincts reporting.

Frank Schubert, manager of the Yes on 8 campaign, declared victory shortly after midnight -- but opponents called that declaration "presumptuous."

"We had more than 100,000 (supporters) walk precincts for us, and they have delivered a great victory," Schubert told supporters.

But Dennis Mangers, co-chairman of No on 8 Northern California Committee, said the outcome of the measure was still in doubt.

"We're absolutely astounded they would be so presumptuous," Mangers said. "I firmly believe that when I wake up in the morning I will find the voters of California said 'no' to discrimination."

While supporters of the measure cited strong voter support in the Central Valley and in pockets of urban areas, opponents noted that half the vote not been tallied.

They pointed out that Alameda County, for example, had yet to report any of its votes, while a third of the precincts in Los Angeles County were still uncounted.

Mangers said that even if opponents lose, they will pursue legal action to challenge the measure.

"We will never surrender our constitutional right to marriage," Mangers said, adding that supporters of gay marriage are prepared to go to the ballot again.

Tuesday's vote on the constitutional amendment came eight years after voters approved a referendum with the same 14 words: "Only marriage between a man and a woman is valid and recognized in California."

That measure, Proposition 22, won resoundingly, 61 percent to 39 percent. But in May, the state Supreme Court ruled that it violated the state constitution's equal protection clause.

Since then, an estimated 17,000 same-sex couples have been married in California, the only state besides Massachusetts and Connecticut to recognize gay unions.

Religious conservatives argued gay marriage is contrary to biblical teachings and cast Proposition 8 as the decisive last stand for traditional marriage.

In television ads blanketing California, the Yes on 8 campaign expanded its argument beyond the question of whether gay couples should be allowed to marry.

Rejection of the measure, they charged, would ultimately lead schools to incorporate same-sex marriage into lesson plans. They said churches refusing to marry same-sex couples would lose their tax-exempt status.

Opponents of the marriage ban dismissed those claims as scare tactics.

Unmarried same-sex couples in California are accorded most of the civil rights heterosexual couples enjoy. But No on 8 forces said banning same-sex marriage would be tantamount to resurrecting long- discredited "separate but equal" policies and laws that barred African Americans and others from marrying whites.

The campaign generated more than $73 million in contributions from every state and more than 20 foreign countries. It set a national record for a spending on a state ballot initiative based on a social issue, according to the Associated Press.

The Yes on 8 campaign – whose chief contributors were members of the Mormon and Catholic churches – raised more than $28 million.

Opponents, led by gay rights groups and labor unions, including the California Teachers Association, raised more than $32 million.

Democratic Attorney General Jerry Brown, in a move initiative supporters called prejudicial, changed the ballot title after the state Supreme Court overturned the gay marriage ban.

In a setback for opponents of gay marriage, a Sacramento judge left intact the ballot title and summary stating that Proposition 8 "eliminates the right of same-sex couples to marry."

Political analysts predicted the new language would make passage of the measure more difficult because voters are generally reluctant to take away existing rights.

After trailing by wide margins in early polls, the Yes on 8 campaign narrowed the gap with TV ads that argued schools would promote gay marriage if the measure failed.

San Francisco Mayor Gavin Newsom, who in 2004 gained national attention when he issued a directive to city officials to issue marriage licenses to same-sex couples, became the face of the marriage ban campaign in mocking ads.

During the campaign, Newsom, a potential Democratic candidate for governor in 2010, officiated at the marriage of a lesbian teacher and her partner.

Call Aurelio Rojas, Bee Capitol Bureau, (916) 326-5545.