The National Organization for Marriage (NOM), the nation's most vociferous opponent of gay marriage, said Friday it was launching a robocall campaign against Tom Campbell, the moderate Republican who supports gay marriage.

Campbell, a former congressman, is vying against former Hewlett-Packard CEO Carly Fiorina and state Assemblyman Chuck DeVore to win the California GOP Senate primary. In a Daily Kos/Research 2000 poll released Friday, Campbell leads his anti-gay marriage opponents by a wide margin: Campbell 37%, Fiorina 22% and Tea Party favorite DeVore 14%.

NOM said was it looking to reach 609,00 likely GOP primary voters with their message.

“The explicit message of this campaign is: don't vote for Tom Campbell, because he supports gay marriage as well as raising taxes,” Brian Brown, president of NOM, said in a statement.

The group began its push to make gay marriage an issue in the race last month when it launched a television campaign attacking Campbell as a cookie-cutter version of Senator Barbara Boxer, a Democrat.

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

This is NOM's first major outing in California since it led the effort to pass Proposition 8 in November of 2008. With a $200,000 campaign, the group also opened a front in Minnesota last week. The ads attack four gubernatorial candidates – three Democrats and one independent – who support giving gay and lesbian couples the right to marry. The ads began airing last Tuesday.

The group is pushing hard to knock Campbell out in the primary because Republicans are generally more sensitive to the issue of gay marriage.

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.”