California will play host this fall to an unprecedented political battle over gay marriage. According to estimates from both camps, a looming ballot-initiative contest will top $30 million in total spending from the rival factions. Even though a proposed constitutional ban on same-sex marriage has not yet made it onto the November ballot, both sides are already taking in big checks from familiar donors.

Adding fuel to the fire are a pair of dueling polls.

Last week, a Los Angeles Times/KTLA  poll found a majority of voters opposed same-sex marriage. But a Field Poll released Wednesday appeared to show a sea change in public opinion on the issue, with roughly half of those surveyed in support of gay marriage. The poll suggests that a constitutional amendment could face a hard road this fall.

Andrew Pugno, an attorney for the Protect Marriage campaign, said his side plans on taking in between $10 million and $15 million -- “a little more than was raised and spent on Proposition 22,” as he put it. That was the 2000 initiative stating “Only marriage between a man and a woman is valid or recognized in California.” It passed with 61 percent of the vote.

This would hardly be record-breaking money for California ballot initiatives, such as the $140 million fight over five amended tribal gaming compacts last year. Nonetheless, the potential spending is huge, Pugno said.

“These kinds of initiatives are different from an insurance industry or tribal gaming measure, where there’s tons of money at stake,” Pugno said. “Because it’s a social issue, it tends to be more of a grassroots thing.”

Steve Smith, campaign consultant for Equality for All, the main group on the “no” side of the proposed Protect Marriage initiative, said his group could raise as much as $20 million.

“We will have to at least match them dollar for dollar,” Smith said.

Where’s all this money going to come from? Oddly, the coalitions on each side look very similar in many ways. Each has a small number of extremely rich donors who were paying attention to this issue long before it was in the news on a regular basis, along with a few key organizations that largely sat out the last round of same-sex marriage fights in 2006. Each side is also taking in hundreds of smaller donations from individuals who will likely provide armies of ground troops working phones and walking precincts.

On the anti-same-sex marriage side, the donors are led by a pair of wealthy Southern California businessmen who are also evangelical Christians. Fieldstead & Co., the company owned by billionaire financier Howard Ahmanson, gave $400,000 in February and March to the committee behind The California Marriage Protection Act. Christian radio magnate Ed Atsinger has donated $12,500. Both live in Southern California. Each man gave $100,000 to back Prop. 22 in 2000.

Meanwhile, the Santa Ana-based National Organization for Marriage has packaged up $921,000 to pass the amendment. Colorado-based Focus on the Family has contributed $133,000. That group’s founder and leader, James Dobson, is one of the leading voices in the anti-gay movement.

Two of the biggest opponents of Prop. 22 have also gotten involved early. The Gill Action fund gave $150,000 to the Equality California Issues PAC in February and March. The Fund is controlled by Tim Gill, the gay founder of Quark Express and a former member of the Forbes list of the 400 richest Americans. The Colorado-based Gill gave a quarter million dollars to fight Prop. 22 in 2000, and is widely seen as a kind of pied piper for gay political donations.

Another openly-gay tech entrepreneur, GeoCities founder David Bohnett, gave $200,000 to the PAC in March. The group Equality for All has put in $815,000, which the Human Rights Campaign has donated $125,000. The National Center for Lesbian Rights added $50,000 in April.

So much money, so early, has caught the eye of analyst Megan Moore of the National Institute for Money in State Politics. She wrote a report on donations to gay marriage ballot measures in 2006 that found those campaigns relied more on individuals and less on organizations.

“The national groups, especially on the gay rights side, have been giving a lot of money,” Moore said. “They had kind of fallen off the radar in 2006.”

There are a pair of factors that may play against the Protect Marriage side. In her report, Moore noted that gay rights groups turned a slight fundraising deficit in earlier years into a $14 million to $4 million advantage in 2006.

While each side has raised in the neighborhood of $1.7 million so far -- not counting donations that have likely flowed in two weeks since the court decision -- the pro-same-sex marriage side has more cash on hand. Much of the money raised by the Protect Marriage campaign, Pugno noted, went to getting signatures to qualify the initiative.

More worrisome for Pugno’s cause is a Field Poll released Thursday morning. It found that likely California voters approved of allowing same sex couples to marry by a 51 percent to 42 percent margin. Depending on how the question is asked, between 51 percent and 54 percent oppose adding a ban on same sex marriage to the state constitution.   

These numbers are the opposite of those found in a Los Angeles Times poll released last week. Field Poll director Mark DiCamillo said that he has a lot of respect for the Times’ polling team -- but that the results of his team’s poll were pretty clear. Voters were still more likely to oppose gay marriage if they tended to be older, less educated, or more religious, conservative and rural.

But over 30 years of polling on the subject, all segments of voters have become more accepting of the idea, he said. Younger voters, meanwhile, make the biggest difference. Among those 18 to 29, 68 percent approve of same sex marriage. Among those 65 and older, it’s just 38 percent.

Both sides see the high stakes as an advantage. Local officials will start signing off on same sex marriages by mid-June. When voters have their say in November, they will essentially be deciding whether to accept or reject these marriages. Prop. 22 had little direct effect, because same-sex couples still couldn’t marry under state law.

Pugno said that Prop. 22 was only polling in the low 50s prior to the March 2000 election, but then did far better when voters actually cast ballots. He also said that many of the younger voters expected to come out this fall will be Hispanic and that Hispanics have been less supportive of same sex marriage than other groups. According to the Field Poll, however, Latinos approved of gay marriage by a 49 percent to 42 percent margin.

His campaign will also try to emphasis how the California law is different from Massachusetts. That court ruling applied only to citizens of that state, and explicitly could not be “exported” to other states. Finally, he said, he isn’t concerned that his side could be swamped by a groundswell of support for likely Democratic nominee Barack Obama.

“I think there is a greater chance of the amendment affecting the presidential election in California rather than the presidential election affecting the initiative vote,” Pugno said, though he added he doubt it would bring the state into play for Republican nominee John McCain.

But DiCamillo said Prop. 22 passed in a kind of “perfect storm” for conservatives: a low-turnout primary election that featured a tight race between GOP presidential candidates McCain and George W. Bush. The Democratic contest had been all but won by Al Gore by that point, he said.

Turnout in that election was 54 percent. But this fall, DiCamillo said, it will more likely hit at least the 76 percent recorded in the last general presidential election held in 2004.

“This will be a much bigger turnout with a much broader mix of voters of all stripes,” DiCamillo said. “If anything, it will be as good of a representation of California as you’ll ever get in an election.”