SACRAMENTO — The No on Proposition 8 campaign unveiled the first ad in the battle over same sex marriage Monday, featuring an elderly couple who urged voters to not eliminate their gay daughter's right to marry.

Prop. 8, on the November ballot, would overturn the state Supreme Court's ruling earlier this year that a ban on same-sex marriage is unconstitutional.

Sam and Julia Thoron, a San Francisco couple who co-wrote the ballot argument against Proposition 8, are featured against the warm backdrop of their home to provide a nonthreatening and familial tone to the message.

They speak of being married for 46 years, and raising three children.

"My wife and I never treated them differently," said Sam Thoron. "We never loved them any differently, and the law shouldn't treat them differently either."

Julia Thoron says: "If Proposition 8 passes, our gay daughter and thousands of our fellow Californians will lose the right to marry. Please don't eliminate that right."

The message plays off what has been a successful theme of the No on 8 campaign: focusing on the rights that would be taken away from gays — rather on the actual issue of same-sex marriage. Polls have shown that voters are strongly opposed to the measure, though they are split on the issue of gay marriage.

Although voters approved an initiative in 2000 that defined marriage as between one man and one woman, a federal court in May ruled that law unconstitutional, effectively granting gays the right to marry.

A spokeswoman for the Yes on 8 campaign said the ad was effective, though a "blatant play for sympathy." And she called it "erroneous," saying no fundamental right for gays to marry exists.

"There's no right for same sex marriage in the U.S. Constitution," said Jennifer Kerns, spokeswoman for the California Marriage Protection Act. "We're entering a dangerous time where four judges think they speak on behalf of millions of California voters.

"They're sick and tired of having their rights infringed upon by the court system that continues to stick it to the voters."

The new ad tries to show a normal couple simply looking out for their children, said Steve Smith, campaign consultant for the No on 8 campaign.

"The reality is that Californians know lesbian and gay couples — they're their neighbors," Smith said. "This defines the issue from the parents' perspective. We want our kids treated the same. We don't think Californians are prepared to hurt them."

Opponents of Prop. 8 say they will be on the air for the remainder of the fall campaign. Their current ad, at a cost of at least $1 million, will run in seven media markets, including the Bay Area.

Both campaigns are well-funded and gearing up for an expensive fall race. The Yes on 8 campaign, which has outraised its opponents $17 million to $11 million, is expected to go up with its own statewide advertising purchase next week, and will likely pound home the theme of an out-of-control judiciary overturning the will of the people.

Reach Steven Harmon at 916-441-2101 or sharmon@bayareanewsgroup.com