SACRAMENTO (AP) _ Candidates seeking to replace Gov. Gray Davis opened the biggest debate of the campaign Wednesday evenly split on whether the recall process that has widely been compared to a circus was good for California.

Actor Arnold Schwarzenegger, participating in his first and only debate so far, hailed the reformist governor who pushed through the recall provision in 1911, while fellow Republican state Sen. Tom McClintock said it was a necessary step when the voters made the wrong decision.

Lt. Gov. Cruz Bustamante who has strayed from his original message of ``no on recall, yes on Bustamante'' returned to his theme and said it was a ``terrible idea'' and bad for democracy. Independent Arianna Huffington criticized the move, but said it was a historic opportunity to elect a progressive, while Green Party candidate Peter Camejo criticized the unusual format that would allow someone to win with a minority of voters.

If nothing else, the unique debate format, in which questions were provided in advance and there was no time limit on answers, provided a spectacle in which candidates jumped on top of each others answers and at times shouted to prevent being drowned out.

The stakes were high for the nationally televised debate: One in five voters in a recent poll was undecided, and two-thirds said they would be swayed by the face-off, which could be the most-watched debate in California political history.

Schwarzenegger set high expectations for his own performance by calling the forum ``the Super Bowl of debates,'' and his rivals in the Oct. 7 recall election were expected to try to challenge him or trip him up.

``This is the opening scene of the third act of the campaign, and it's a referendum on Arnold,'' said GOP strategist Allan Hoffenblum. ``He needs to come across as competent, that he has command of public policy issues and that he appears qualified to be governor. If he does all that, he'll win.''

The GOP front-runner faced Democratic Lt. Gov. Cruz Bustamante, Republican state Sen. Tom McClintock, independent Arianna Huffington and Green Peter Camejo in the evening debate at California State University, Sacramento.

The candidates were given a dozen questions in advance on such topics as how to balance the budget, the meaning of a colorblind society and services for senior citizens.

The campaign was put back on track Tuesday when a federal appeals court reversed course and unanimously ruled the election could go ahead next month despite the risk of confusion from the use of punch-card ballots in some counties.

At least 500 representatives from more than 100 media outlets around the world covered the debate, said the organizers, the California Broadcasters Association.

The scripted format prompted criticism, particularly among Schwarzenegger opponents who said he has been deliberately dodging more spontaneous candidate forums.

Schwarzenegger did not take part in debates held on Sept. 3 and Sept. 17. Although another major debate is set for Sept. 30, Schwarzenegger's campaign said the intention was to attend only Wednesday's.

For Schwarzenegger, part of the challenge was to solidify his position as the GOP front-runner in order to increase pressure on McClintock to drop out of the race. Many GOP leaders worry Republicans risk splitting their votes between the two candidates and throwing the election to Bustamante. A strong debate performance by McClintock, however, could strengthen his resolve to stay in the race, analysts said.

In a poll last week by the Public Policy Institute of California, 67 percent of likely voters said the debate would influence their vote. The poll also showed that one in five voters remained undecided about whom to support if Davis is recalled.

The debate comes as the campaign has taken a distinctly negative turn. On Monday, Schwarzenegger broke a vow to stay positive, and began airing a television commercial attacking Davis and another taking aim at the state's powerful Indian gambling tribes and implicitly criticizing Bustamante and McClintock for taking large tribal campaign contributions. On Tuesday, Bustamante hit back with an ad that called Schwarzenegger an elitist outsider from ``Planet Hollywood.'' On Wednesday, Schwarzenegger released a new radio ad attacking tribes that criticizes Davis, Bustamante and McClintock by name.

``If there is a real shootout at the debate, it can only help Davis,'' said Republican political strategist Arnold Steinberg. ``Davis has to hope everyone does badly here, including Bustamante.''

Davis, who is not participating in the debate, was the target of new attacks from Schwarzenegger as well. In an essay Wednesday on the editorial page of The Wall Street Journal, Schwarzenegger wrote that Davis ``has created a counterproductive culture in Sacramento where businesses and entrepreneurs that dare make a profit are treated as if they are enemies of the state.''

Davis said he hadn't yet decided how to respond to Schwarzenegger's attacks, but said a decision would come soon.

``I will tell you this: His ads say more about Mr. Schwarzenegger than they do about anyone else,'' Davis said. ``He said he would not take special interest money, and now he's taking it. He said he would not run attack ads, now he has. He said he'd debate people, but now will only do it if he gets the questions in advance.''