SAN FRANCISCO - Five months and thousands of weddings after California's highest court sanctioned same-sex marriage, anxious eyes around the nation will closely follow voters Tuesday as they decide whether to turn back the clock.
Given the state's size and influence, the vote on a constitutional amendment banning gay marriage has become a referendum on sexual orientation and civil rights. Both sides call it the "Gettysburg" of the power struggle between the gay rights movement and the Christian right, with the victors capturing momentum in other states.
"As California goes, so goes the nation," Mayor Gavin Newsom boldly predicted at a City Hall celebration the day the state Supreme Court legalized marriages of gays and lesbians.
The race has tightened over the last six weeks and is expected to be close. A Field Poll released Friday found 49 percent of likely voters oppose the ban and 44 percent favor it. In mid-September, the measure was losing by 17 points.
"In the minds of many people, Proposition 8 is the most important thing nationally on the ballot," said Tony Perkins, president of the Washington-based Family Research Council, which supports the measure. "We have survived bad presidents. But many, many are convinced we will not survive this redefinition of marriage."
Religious and civil rights groups, wealthy philanthropists and middle-class donors have poured $69 million into campaigns for and against Proposition 8, making the initiative the most expensive election question this year outside the race for the White House. Almost $21 million has come from campaign contributors outside California.
Even the presidential candidates weighed in on Proposition 8: Sen. John McCain endorsed it and Sen. Barack Obama opposed it. Former President Bill Clinton recorded a telephone message that went to millions of California households Friday asking voters to defeat the measure.
The majority of opinion leaders in the state, including almost every major newspaper, the League of Women Voters, the state NAACP, and moderate politicians such as Gov. Arnold Schwarzenegger and U.S. Sen. Dianne Feinstein oppose the measure, which critics say unfairly denies one group a basic right.
Corporations that normally shy from contentious issues also have come out against it. The founders of Google, Yahoo and Adobe Systems took out a newspaper ad Friday encouraging Silicon Valley residents to reject it.
"This is the most intense and expensive social issues fight we have ever seen. And I think the real reason is because it's very rare in American life (that) we have ever put existing rights on the ballot," said Patrick Guerriero, a former leader of the gay Log Cabin Republicans who now directs the "No on 8" campaign.
But the measure's opponents have found a formidable foe in the coalition of religious and social conservatives who sponsored the initiative. Since leaders of the Utah-based Church of Jesus Christ of Latter-day Saints appealed to members to back the ban, Mormon dollars and volunteers have streamed into California.
L. Whitney Clayton, the church's liaison with a coalition called ProtectMarriage.com, said the religious right and Mormons see a threat to the fundamental underpinnings of their faiths.
"The impact upon society over the long run is something that makes people very apprehensive," Clayton said. "What will our children be taught in school? What will happen to the freedom of religion? What will people be able to preach and believe, and will they be able to do the things that they are accustomed to doing?"
California Roman Catholics, at the urging of bishops, also have stepped up with money and manpower, as have evangelical Christians.
The initiative's backers contend that people of faith will be forced to embrace same-sex marriage if the ban loses, and teachers will be required to inform children about gay relationships, an assertion denounced by state education officials. They also argue that opponents of same-sex marriage are unjustifiably being painted as bigots.
The measure, which would change the California Constitution to limit marriage to a woman and a man, marks the first time voters have been asked to ban same-sex unions retroactively. If passed, it would overrule the state Supreme Court decision in May that said preventing gays from marrying was unlawful discrimination.
Many couples have hurried to tie the knot before Election Day despite uncertainty over whether their unions would remain valid if voters approve the measure. Attorney General Jerry Brown has already opined that the ban would not be retroactive, but legal scholars have expressed uncertainty and said the matter would almost certainly be litigated.
Beyond what that might mean for already married couples, the measure's adoption or rejection could affect the pace at which other state courts and legislatures move to legalize same-sex marriage. Depending on how the vote goes, it could also reinvigorate efforts to get Congress to consider a law extending nondiscrimination workplace protections to gays and lesbians or a federal constitutional gay marriage ban.
Gay couples are expected to begin marrying this month in Connecticut, the third state after Massachusetts and California to allow same-sex weddings. The Iowa Supreme Court is set to hear arguments in a similar case next month. Meanwhile, gay rights activists have been lobbying lawmakers in New York, New Jersey and New Hampshire to take up marriage legislation.
"If those who favor man marrying man were to win in California, it would be a big boost to their movement and a big loss to our efforts to preserve the definition of marriage as its always been known in our country and Western civilization," said Tim Wildmon, president of the Mississippi-based American Family Association.
A setback for same-sex marriage in California would deprive the gay rights movement of the opportunity to show mainstream America what happens when gay couples can marry, said Joe Solmonese, president of the Human Rights Campaign.
"No matter where you sit in this country, it moves the hearts and minds of all when we have a big slice of the nation to watch and see gay people can get married and not one thing has changed," Solmonese said. "Those dire warnings about the end of the world as we know it just aren't coming true."