The National Organization for Marriage is pushing to make gay marriage an issue in the upcoming California GOP Senate primary.

The nation's most vociferous opponent of gay marriage is spending $300,000 in the state on ads attacking moderate Republican candidate Tom Campbell.

“Tom Campbell says he'd be a better senator than liberal Barbara Boxer, but is he really much different?” a female announcer says in a television ad.

“Tom Campbell supports gay marriage and opposed Proposition 8,” a male announcer says, referring to California's voter-approved gay marriage ban. “Barbara Boxer supports gay marriage and opposed Prop. 8,” the female announcer adds.

“Two peas, same liberal pod,” the pair say.

Campbell, a former congressman, is vying against former Hewlett-Packard CEO Carly Fiorina and state Assemblyman Chuck DeVore to win the Republican nomination. In a recent Public Policy Institute of California poll, Campbell and Fiorina, who says she believes marriage should remain solely a heterosexual union, are running nearly even.

NOM says it can wrench primary votes away from Campbell because the majority of Republicans are unaware that he supports gay marriage.

“Voters want politicians with the courage to stand for their values, not the values of San Francisco,” Brian Brown, executive director of NOM, said in a statement. “We know that Californians, especially GOP primary voters, are going to be asking who will be on their side for the tough fights ahead. As ordinary Californians were standing tall for marriage in the face of enormous pressures, harassment and name-calling during the Prop. 8 battle, Tom Campbell was nowhere to be found. Or rather, he was to be found standing hand-in-hand with [Democrat] Barbara Boxer.”

This is NOM's first major outing in California since it led the effort to pass Proposition 8 in November of 2008.

Over the past year, the group has also influenced races in New York, Massachusetts and Iowa, where it supported candidates based on the single issue of gay marriage, at times over the objection of the Republican Party.

“Our goal is not to necessarily elect Republicans,” Brown told The Associated Press. “Our goal is to elect candidates who will stand up and protect marriage.”

Both Fiorina and Campbell appear to be ignoring the marriage ruckus for now. Fiorina does not list the issue on her website and Campbell says it's a non-issue.

“I'm telling you straight: Whenever I go out and speak, I get questions on unemployment, inflation, interest rates, the Central Valley being cut off from water,” Campbell told attendees at the California Republican Party convention in early March. “I don't get the social questions, and I think that's a sign of the importance of the economic issues.”

Dan Brown, president of the San Francisco chapter of the gay group Log Cabin Republicans, agreed.

“I really don't think most of the voters in California are one-issue voters, and that is what the National Organization for Marriage is trying to imply,” he told gay weekly The Bay Area Reporter.

But gay rights groups in the Golden State know better than to outright discount the group's influence among social conservatives. NOM is often credited for getting Proposition 8 on the ballot in California and helping Republican Scott Brown win the seat of former Massachusetts Senator Ted Kennedy. And while nobody is certain how deep the group's pockets go, deep they are.