A handful of California Republicans vying to face Sen. Barbara Boxer (D) in 2004 will get an early informal test in June as moderate Golden State GOP officials hold their annual gathering north of Santa Barbara.

As has been the case for the past four years, centrist Republicans will meet the weekend of June 13-14 at the ranch of former state Assemblyman Brooks Firestone to plot strategy and vet potential candidates.

Organizers of this year’s event have invited five possible Senate hopefuls to speak — Rep. Doug Ose, Rep. George Radanovich, U.S. Treasurer Rosario Marin, ex-Gov. Pete Wilson and U.S. Small Business Administration official Toni Casey. Their speeches will be followed by a straw poll to gauge the reaction of attendees.

Firestone said that the straw poll “is an early indication of support,” though he allowed that the poll is informal and thus “not very important” in the long term.

What is important to Firestone and many other California Republicans is the nomination of a candidate to face Boxer who hails from the moderate wing of the party. “It is absolutely crucial,” Firestone said. “It is the mainstream of California.”

Ose and Radanovich have so far been the most aggressive Senate candidates, though Marin has recently stepped up her public appearances and has taken to criticizing California Gov. Gray Davis (D).

Casey is currently the head of intergovernmental affairs for the Small Business Administration. Before she was appointed to that post in 2002, she was mayor of Los Altos Hills, a town in Silicon Valley.

Wilson, who served in the Senate for eight years before holding the governorship from 1991 to 1999, has been mentioned in some Republican circles as ripe for a comeback. An independent poll released last week showed him trailing Boxer in a head-to-head matchup by just 3 points.

Despite that, most California GOP observers have said that they do not expect Wilson to run. The same is likely true of GOP Reps. Darrell Issa and Mary Bono as well as actor Arnold Schwarzenegger.

Firestone’s gathering last year came in the midst of a heated gubernatorial race during which conservative businessman Bill Simon (R) was unable to defeat Davis despite the incumbent’s low approval ratings. Many centrist Republicans have argued that the party should have nominated one of their own for that race and took the result as evidence that the 2004 Senate nominee must be a centrist.

In addition to the Senate straw poll, the June meeting will also feature speeches by Gerald Parksy, the financier who is President Bush’s closest ally in the state, as well as new state Republican Party Chairman Duf Sundheim.