The 9th U.S. Circuit Court of Appeals ruled that the election cannot proceed as scheduled because some votes would be cast using outmoded punch-card ballot machines. The decision applies to all the recall questions on the ballot, as well as two propositions.
The court, the nation's largest and most liberal federal appeals court, withheld ordering the immediate implementation of its decision by a week to allow time for an appeal to the U.S. Supreme Court.
It is the same court that ruled last summer that reciting the Pledge of Allegiance in public schools is unconstitutional because of the words "under God" inserted by Congress in 1954.
Ted Costa, head of the Sacramento-based Peoples' Advocate, one of the groups that put the recall on the ballot, said an appeal of Monday's ruling was certain. "Give us 24 hours," he said.
CBSNews.com Legal Analyst Andrew Cohen says the appellate court ruling "is based on the notion that election officials cannot treat voters in different counties differently just because of the ballots they use, especially when those differences creating different patterns of voting error."
Cohen says that may make it "difficult for the Supreme Court to reverse the ruling because it seems to track what the justices decided in their famous Bush v. Gore ruling after the 2000 presidential election."
Gov. Gray Davis said he expected an appeal.
"This recall has been like a roller coaster. There are more surprises than you can possibly imagine," Davis said after appearing with former President Clinton at a school dedication. "I'll continue to make my case to the people that a recall is not good for them."
Arnold Schwarzenegger, the leading Republican among the 135 replacement candidates, issued a statement calling on the secretary of state to file an appeal on behalf of Californians.
"Historically, the courts have upheld the rights of voters, and I expect that the court will do so again in this case," Schwarzenegger said. "The people have spoken, and their word should, and will, prevail."
Secretary of State Kevin Shelley, a Democrat, wouldn't say when he would decide on a possible appeal.
The ruling is likely to benefit Davis if the election is delayed to the next regularly scheduled primary, March 2.
The March presidential primary is expected to draw large numbers of Democratic voters, and the months until then would give Davis more time to address the state's problems and force Schwarzenegger into a longer campaign.
The decision came as the race's top names were enlisting big national stars in their campaigns.
Trying to soften his image with women voters, Schwarzenegger assured talk show host Oprah Winfrey on Monday that reports of a salacious, party-hard past were more tall tale than truth and do not bear on his run for California governor.
Davis was in Southern California with former President Clinton to dedicate the William Jefferson Clinton elementary school in the impoverished suburb of Compton, and the two had planned to later attend a fund raiser.
In the ruling Monday, the judges of the 9th Circuit agreed with the American Civil Liberties Union that the punch-card voting machines still used in six California counties are prone to error.
The counties — Los Angeles, in addition to Mendocino, Sacramento, San Diego, Santa Clara and Solano — were already under a separate court order to replace them by the March primary, but the machines wouldn't be replaced in time for an Oct. 7 special election.
"In sum, in assessing the public interest, the balance falls heavily in favor of postponing the election for a few months," the court said.
Schwarzenegger and his wife, television journalist Maria Shriver, were in Chicago on Monday morning taping the season premiere of "The Oprah Winfrey Show." Polls had showed the actor struggling to win over women in the recall race, and women are the show's primary audience.
Schwarzenegger, speaking before the court ruled, told Winfrey he was excited about the campaign. He also talked about old magazine articles that had resurfaced in which he described a sexually salacious, party-hard lifestyle and said they reflected a 1970s strategy to pump up interest in body building, the sport that made him famous.
"We really were out there doing crazy things. We were trying to get the attention," he said. "At that time I didn't think I was going to run for governor."
Before Schwarzenegger took the stage, Winfrey asked Shriver — a member of the Kennedy family — whether she had been brought up to look the other way if her husband was a womanizer.
"You know that ticks me off," Shriver said. "I am my own woman, I have not been bred to look the other way. I accept him with all his strengths and all his weaknesses, as he does me."
Davis, meanwhile, made a second day of campaign stops with Mr. Clinton, following a joint appearance Sunday at a predominantly black church in Los Angeles.
Mr. Clinton had spoken passionately against the recall during the Sunday service, mixing Scripture with politics at the First African Methodist Episcopal Church.
He repeated his party's theme that the recall election is part of a right-wing power grab, and said removing Davis could scare future officeholders away from making difficult choices.
"This is way bigger than him," Mr. Clinton said. "It's you I'm worried about. It's California I worry about. I don't want you to become a laughing stock, or a carnival, or the beginning of a circus in America where we throw people out for making tough decisions."
"Don't do this. Don't do this," he said. The congregation erupted in applause.
Davis was also scheduled to campaign this week with other prominent Democratic figures, including former Vice President Al Gore, the Rev. Jesse Jackson and several of the 2004 Democratic presidential candidates.