LONG BEACH - One of the main secular arguments in favor of keeping same-sex marriage legal has been economic.

More weddings - gay or straight - mean more work for event planners, bartenders, florists, hoteliers and others in hospitality and tourism.

But few realized that gay marriage would be so good for political consultants, television stations, printers and others on the business side of politics.

Proposition 8, the proposed ban on same-sex marriage, is shaping up to be one the costliest ballot measures on a cultural issue in state history, experts said Tuesday.

Those on either side of the referendum have raised $41.2 million, the Associated Press reported. One estimate said the combined number was likely to grow to $50 million by the Nov. 4 election.

Those in favor of the ban raised $25 million to opponents' $15.8 million, according to the A.P.

"I am going to be hard-pressed now to think of a social issue that has raised more money than this one," said John Matsusaka, president of the Initiative and Referendum Institute at USC. "The only ones that get to this level are ones that involve wealthy industries like gambling, oil, tobacco and insurance."

He added that the fund-raising for and against Proposition 8 has been impressive since neither side has much of a financial stake in the outcome.

"This issue, for many people, gets right into the core, it gets right into what they think the foundation of our society is going to be," he said. "This isn't a peripheral issue like abortion. This is marriage, which is really the center of our society."

By comparison, California's highly charged Proposition 187 of 1994 raised about $3.2 million from those who supported curtailing benefits to illegal immigrants and about $1.6 million from those against.

Matsusaka said every initiative banning same-sex marriage has won nationwide, save for a proposal in Arizona that wasn't exactly comparative because it also curtailed domestic-partner benefits.

However, the professor said he doubts Proposition 8 will pass because it started out so far back in the polls, and generally ballot initiatives must begin strong and gather momentum to keep voters' attention.

"You have to convince voters to move away from the status quo," he said. "They are going to stick with what they have unless you give them reason not to."

Though the measure trailed earlier in the respected Field Poll, Proposition 8 was said to be leading by about 5 points with 10 percent of voters undecided in a poll released this week by a San Francisco CBS affiliate.

Proposition 8 supporters said they are happy to be leading in both the new poll after starting 10 to 15 points behind opponents, as well as fund-raising.

"We are thrilled, as you can imagine," said Sonja Eddings Brown, deputy communications director for Protect Marriage California. "We feel these impressive numbers reflect the strength of our cause, the commitment of the people of California to stand up for traditional marriage, and the success of the campaign."

Geoff Kors, spokesman for Equality California, which opposes Proposition 8, said his organization's internal polling showed the measure ahead by 4 points.

He said recent television ads by Yes-on-8 side and an infusion in cash quickly showed up in the polls and hurt the No-on-8 campaign.

"I think their massive media buys filled with lies and distortions were effective," he said.

Despite perceptions that Proposition 8 is being funded largely with out-of-state money, Brown said about 97 percent of the donations have come from within California.

Key to defeating the measure, Kors said, is for members of the sizeable gay and lesbian community in Long Beach and elsewhere in the state to donate money toward stopping Proposition 8.

"We need to close that gap," he said of the $10 million difference in funds raised. "We've always said that if we can compete dollar for dollar and get on equal footing, we would win.

"We believe we can turn that around, and we believe California voters aren't going to vote to eliminate a fundamental right for one group of people."

john.canalis@presstelegram.com, 562-499-1273.