San Jose ? The pummeling of former Los Angeles Mayor Richard Riordan, who is the front-runner in the March 5 Republican gubernatorial primary and is leading Democratic Gov. Gray Davis in the polls, began an hour before he stepped on stage to face his two opponents in Saturday’s Republican state convention debate here.

Former Gov. George Deukmejian, supporting another contender, Secretary of State Bill Jones, told a news conference that if Riordan becomes the GOP nominee, “I would not vote for him. I have no respect for the man.” Riordan had loaned and given six-figure amounts to Deukmejian’s Democratic opponent, the late Tom Bradley.

Deukmejian’s comment triggered the first question from the debate panel of reporters, and Riordan compounded his problem by saying in what he later insisted was a joke that it was too bad Deukmejian’s memory is so bad, “he remembers only his grudges.”

The boos from the audience of Republican activists showed how badly Riordan had misstepped, and he offered his apologies in a post-debate news conference.

That was actually his third apology of the afternoon. During the debate, he said he was sorry he had given $1,000 to liberal Democratic Rep. Maxine Waters in an earlier election and regretted having called abortion “murder” in a 1990 TV interview. Davis is using that tape as part of an extraordinary early ad assault on Riordan.

Davis’ $1.5 million-a-week effort aims to depict the only avowedly pro-choice Republican candidate in this pro-choice state as a hypocrite on the issue. Pollsters in both parties say it has been damaging. But Riordan is trying to turn it to his advantage in the primary.

His opening statement in the debate was, “My fellow Republicans, Gray Davis is spending millions to beat me in the Republican primary because he knows I will beat him in November.” That line drew cheers, but from then on it was downhill for Riordan, as Jones and the third candidate, William Simon Jr., son of the Nixon administration treasury secretary, took turns assailing Riordan for his past financial help to Democrats and his scattershot but suspiciously liberal positions as businessman-mayor of Los Angeles.

The remarkable thing about this contest for the No. 1 prize in the No. 1 state is how past actions shadow the chances of all three Republicans and of Davis, who could be the first incumbent governor denied a second term in 60 years.

Even Democrats who think tradition and Davis ultimately will prevail concede he looks very vulnerable. Democratic focus groups find he gets little credit for his education efforts, and Republicans say voters overwhelmingly think the economy, transportation, education and especially energy costs have become worse in the last three years. Already suffering from a perceived leadership gap, Davis now faces a budget shortfall that may be much larger than his $12 billion estimate.

His effort to pursue a middle-ground course has cost him support among traditional Democratic constituencies. Davis’ consultant, Garry South, concedes that “part of our problem is getting our Democratic base back with us.”

Jones argues that he has attracted Democratic crossover votes in his two successful races for secretary of state, surviving the Democratic sweep of other statewide offices in 1998, even though he is a self-described conservative and the author of the three-strikes law. But Jones committed political heresy in 2000, switching his support from George W. Bush to John McCain, and the president’s many friends have shut down Jones’ money, forcing him to pin his slim hopes on grass-roots support in his native Central Valley and a final-week shot of TV ads.

Private polls say Simon has moved ahead of Jones as Riordan’s main challenger, even though the wealthy financier and novice candidate is still unknown to most Republican voters. He matches Jones’ conservative positions and has used an endorsement ad from Rudolph Giuliani for whom he worked as an assistant prosecutor decades ago to identify himself. But with his tight-lipped smile and Dick Tracy demeanor, Simon is anything but a comfortable candidate. And he too has a past embarrassment: Since moving to California, he has rarely bothered to vote in Republican primaries.

All of which should make it easy for Riordan were it not that he has been so promiscuous a contributor to Democratic friends (as well as Republicans) and so prone to making comments that require clarification. Almost daily, he provides new openings for his opponents.

Republicans are desperate to defeat Davis, but must swallow hard to nominate a man who despite the inroads he might make in Davis’ Los Angeles vote base has an activist Democratic wife and a campaign team that includes such longtime Democrats as McGovern/Carter pollster Patrick Caddell and Dukakis campaign manager Susan Estrich.

A very strange race.

David Broder is a columnist for Washington Post Writers Group.