LOS ANGELES - Arnold Schwarzenegger, the former Mr. Universe who became a millionaire superstar in Hollywood action movies, announced yesterday that he would run for governor of California, setting the stage for a tumultuous two-month campaign to unseat Democratic incumbent Gray Davis.

The Republican actor, best known for playing a killer robot in three Terminator movies, opened his campaign with a raw display of the extraordinary national media platform at his disposal, announcing his candidacy on NBC's Tonight Show With Jay Leno.

His move into the race capped a day that set the state's political universe reeling, one that began with U.S. Sen. Dianne Feinstein, a Democrat, firmly taking herself out of the race.

Feinstein, in a statement and later interviews, characterized the two-month recall campaign as a carnival that would distract from the serious issues facing the cash-strapped state.

"After thinking a great deal about this recall, its implications for the future and its misguided nature, I have decided that I will not place my name on the ballot," she said.

Even Davis strategists had conceded that the governor would lose the two-part recall election if Feinstein agreed to place her name on the ballot. The recall will first ask voters whether they wish to recall Davis; they will then be asked to vote on a replacement.

Her departure from the race, while denying it the state's most popular and prominent politician, did nothing to stem the seepage on the Democratic side.

As the day wore on, several state officeholders were weighing a jump into the race. Chief among them was Lt. Gov. Cruz Bustamante, who as late as Tuesday had insisted he would not be on the ballot.

Richie Ross, Bustamante's political consultant, confirmed that the lieutenant governor is poised to declare his candidacy: "I think he's going to do it."

He said Bustamante has scheduled a news conference for this morning.

Slight family tiff

Also joining the race yesterday was author and newspaper columnist Arianna Huffington, an independent whose ex-husband, former Republican Rep. Michael Huffington, is also considering whether to join the race.

She had said last week that she would stay out if her ex-husband decides to run, a comment that prompted a sort of public spat yesterday between the former spouses.

"Obviously, Arianna has initiated her campaign with a lack of credibility," said Michael Huffington's spokesman, Bruce Nestande, who said the former congressman had not decided whether to run.

Today, Republican U.S. Rep. Darrell Issa, who bankrolled the recall effort, and Peter Camejo, the Green Party gubernatorial nominee last year, plan to file papers to put their names on the ballot.

But the entrance of Schwarzenegger dwarfed all others. It came as a particular surprise not only to the state's political class but to the audience at the Tonight Show, which burst into applause at the news.

Casting himself as a man of the people who would challenge special interests in the state Capitol, Schwarzenegger promised to "clean house" in Sacramento.

"The people are working hard," he told Leno in his trademark Austrian accent.

"The people are paying the taxes, the people are raising the families, but the politicians are not doing their job. The politicians are fiddling, fumbling and failing."