Marilyn Brewer (R) is betting more than $600,000 that there are a lot of liberal Orange County Republicans — enough, at least, for her to beat state Sen. John Campbell (R) and 15 other candidates in the race for California’s open 48th district seat.

Vacated by former Rep. Christopher Cox (R) this year when he was appointed Securities and Exchange Commission chairman, the 48th district gave

the anti-abortion rights, stem-cell research cautious and anti-prescription drug importation President Bush 58 percent of the vote last year to Sen. John Kerry’s (D-Mass.) 40 percent.

But Brewer, a former state assemblywoman, has played up her Kerry-esque positions — pro-abortion rights and supportive of importing prescription drugs from Canada and loosening restrictions on stem-cell research — in her bid to win the Republican nomination in Tuesday’s special open primary election.

“We were surprised at how moderate the district has become,” said Brewer campaign spokesman James Vaughn.

In an election where voters can choose any candidate they want regardless of party registration and the top votegetter in each party moves on to a Dec. 6 runoff if no one gets more than 50 percent of the vote, it sounds like Brewer might have a winning strategy, especially if she is able to attract votes from Democrats and independents. She already has been the beneficiary of high-profile endorsements from Sen. John McCain (R-Ariz.) and former New Jersey Gov. and Environmental Protection Agency Administrator Christie Todd Whitman (R).

Brewer’s campaign Tuesday also was aided by a $100,000-plus radio ad buy and direct-mail campaign by the Republican Main Street Individual Fund, a 527 group that supports moderate Republicans, accusing Campbell of flip-flopping on illegal immigration.

However, it’s difficult to find a knowledgeable observer of Orange County politics who thinks the 48th district is anywhere near as liberal as Brewer’s campaign says it is.

Allan Hoffenblum, a Republican consultant and publisher of the California Target Book — California’s version of The Almanac of American Politics — said it would be a real upset if Brewer won.

“It’s an open primary. If this was a closed GOP primary I’d be surprised if Brewer was in the race,” Hoffenblum said. “Even now people believe this is Campbell’s campaign to lose.”

Campbell, who has raised nearly $850,000, is running ads on cable television through Election Day and is planning a ground assault on the district during the campaign’s final four days.

About 250 people, including Republican volunteers based in Washington, D.C., are scheduled to walk precincts. Absentee voters have been targeted since mid-August, and the Campbell campaign called it a “good sign” that 65 percent of the 20,000 ballots mailed in so far were submitted by Republicans.

For Campbell, the goal isn’t just winning, but winning with 50 percent plus one of the vote and avoiding a runoff. The Campbell campaign’s internal polling shows him winning the most votes and sending Brewer home, though whether he can avoid the runoff remains in question.

“Our goal is to try and get to 50 percent. Most people don’t think we’ll be able to,” said Campbell’s chief strategist Dave Gilliard. “I think it’s very difficult.”

If any candidate is standing in the way of Campbell walking away with the seat on Tuesday, it’s Jim Gilchrist, founder of the Minutemen Project, a group of volunteers that has patrolled the Mexican border in an effort to thwart illegal-alien crossings.

Gilchrist, running as the only candidate under the American Independent Party banner, is guaranteed to make any runoff, regardless of how many votes he receives.

Although he sent a letter to Speaker Dennis Hastert (R-Ill.) on Monday announcing his intention, if elected, to vote with the Republican caucus, and pledging to work on a wide variety of GOP issues, Gilchrist clearly is trying to ride a wave of discontent over illegal immigration into office.

“The Republican leadership is more concerned with getting votes and keeping themselves in power than following the law” on immigration, said Gilchrist campaign manager Howie Morgan.

Gilchrist’s plan, Morgan said, is to take enough of the conservative vote away from Campbell to force a runoff. Having raised around $200,000, Gilchrist intends to spend money on television and radio ads, with precinct walks planned, between now and Election Day. On Tuesday he was endorsed by Rep. Tom Tancredo (R-Colo.), popular among those who favor clamping down on illegal immigration.

Hoffenblum expects Gilchrist to get anywhere from 9 percent to 11 percent of the vote. The unknown: Will the rest of the field, minus Brewer, eat up enough votes to force Campbell into a runoff?

Attorney Steve Young, a Democrat, is the only other candidate running a serious campaign. But even if the 13 remaining candidates attract 2 percent of the vote each, that’s 26 percent total, decreasing Campbell’s chances of avoiding a runoff.

“If the other 13 only take half a percent each, maybe we could do it,” Gilliard said.

Voter turnout is the other wildcard in the race. Only 17 percent of registered voters turned out for a recent special election to fill an open state Assembly seat that represents a southwestern portion of Los Angeles County.

A low turnout Tuesday should benefit Campbell, as the majority of voters in such elections tend to be political partisans, as opposed to moderates and independents.

In this case, that would mean the majority of voters are committed Republicans who pay attention to the fact that Campbell has received the backing of the Orange County and California Republican parties, as well as that of Gov. Arnold Schwarzenegger (R).

Campbell also received the endorsement of the Lincoln Club of Orange County, and Rich Wagner, the group’s president, said the state Senator embodies the kind of Republican candidate voters in the 48th tend to support.

“This district is a very sophisticated district, in that you have a lot of very highly educated people,” Wagner said.

“They own companies; these people are very attuned to what’s going on with respect to the economy and financial markets so when you have guy running that’s been at the forefront of being critical of job killing legislation coming out of Sacramento, what you have is a very popular individual.”