The still-unofficial race to succeed Rep. Christopher Cox (R-Calif.) has undergone several jolts in the past few days, with the leading candidate abruptly dropping out Monday and a new frontrunner emerging.

State Senate Minority Leader Dick Ackerman (R), who had racked up numerous key endorsements in the days following Cox’s June 2 nomination to head the Securities and Exchange Commission, said Monday that he would not run for the Congressman’s Orange County House seat after all.

Ackerman’s announcement came after state Sen. John Campbell (R) jumped into the special election Friday — just a week after endorsing Ackerman — taking Ackerman’s political consultant along with him. Campbell, a millionaire car dealer who was just elected to the Senate last year, is now considered the man to beat whenever a special election is called after the Senate confirms Cox.

“It became clear with John Campbell getting in that this would be a full-time campaign, and I wouldn’t have time to work on other things in the upcoming months,” Ackerman said in a statement.

The stunning turn of events was precipitated at least in part, according to several sources, by a spat between Ackerman and Campbell immediately following Ackerman’s decision to enter the Congressional race. Campbell had hoped to succeed Ackerman as Senate Republican leader, the sources said, but was thwarted when another Senator quickly sewed up the necessary votes.

In an interview, Campbell said he changed his mind about the Congressional election after hearing from several supporters in the days after he endorsed Ackerman and discussing the matter one last time with his family.

“I made the wrong decision” initially, he conceded.

Ackerman’s camp is dismissing the notion that the Minority Leader, who is not known as an aggressive fundraiser despite his institutional clout, was chased out of the race by Campbell’s personal wealth — or by the fact that Gilliard, Blanning, Wysocki and Associates, a prominent GOP firm in Sacramento that has worked for both men, had decided to go with Campbell in the Congressional race.

Ackerman, who will remain as party leader, “likes Sacramento,” said Adam Probolsky, the Senator’s pollster. “He likes being in the Big Five [of state officials]. And he’s good at that.”

But the Gilliard firm’s defection from Ackerman has sparked considerable buzz in California political circles. Just a week ago, partner Chris Wysocki had traveled to Washington, D.C., to meet with Republican Members and party leaders on Ackerman’s behalf.

Campbell said he expects to visit D.C. in about two weeks.

In addition to Ackerman’s departure from the race, Campbell received further good news Monday when another potential candidate, former state Sen. John Lewis (R), who has been working as a political and corporate consultant for the past four years, announced that he would not run.

Lewis, who has close ties to several prominent elected officials in Orange County, would likely have drawn votes from the same pool of conservative supporters as Campbell.

But Campbell does not have the Republican primary field to himself. Former state Assemblywoman Marilyn Brewer (R), a moderate Republican who supports abortion rights, continues to prepare for the race, fueled by a $150,000 check she wrote herself last week.

Harvey Englander, a consultant for Brewer, said Ackerman’s departure and Campbell’s emergence as the frontrunner have little impact on his candidate’s thinking and should actually boost her prospects.

“All these people who endorsed Ackerman and said he was the greatest thing since sliced bread are now going to have to re-evaluate,” Englander said.

Englander said that if the special Congressional election coincides with the November statewide special election, Brewer could benefit from a higher level of voter turnout. She has promised to put in more than the $150,000 seed money she has already committed to her campaign.

But Campbell could also contribute heavily to his effort. In 2004, when he was a state Assemblyman, he spent about $1.2 million — including more than $50,000 from his own pocket — on a competitive state Senate primary against a fellow assemblyman.

“I will self-fund,” Campbell said. “How much, I don’t know at this point.”

But money may not be Campbell’s only advantage in the race. He is considered aggressive and articulate. He comes from a prominent Republican family: His father was part of Ronald Reagan’s extended kitchen cabinet when Reagan was governor of California.

“People are coming to the conclusion that John Campbell is a very formidable candidate,” said Jon Fleischman, a former executive director of the California GOP. “And he’s very much in the Chris Cox model.”

Asked whether Republicans who supported his bid for state Senate last year would hold his Congressional ambitions against him in 2005, Campbell said no.

“They’ll know that it’s not like I had this in the plan,” he said. “The opening in the Cox seat has been a big surprise to everybody.”

Many political observers expect further surprises before the special election is officially called.

One could be the entry into the race of James Gilchrist, leader of an anti-immigration group that has stationed armed sentries along the U.S.-Mexico border.

Gilchrist, who according to Fleischman is not a registered Republican but is instead a member of the American Independence Party, has told associates that he is contemplating the race. Gilchrist is scheduled to speak to a prominent Orange County GOP group on Thursday. In an open primary, he could attract many conservative Republican and independent voters.

Meanwhile, former Rep. James Rogan (R-Calif.) continues to be seen as a possible late entry into the race. But ex-Rep. Bob Dornan (R-Calif.) is now considered unlikely to run.

“There have been some pretty dramatic ebbs and flows in this race already,” Probolsky said. “I’ve got to assume that we’ll have one or two more.”