LOS ANGELES (AP) — U.S. Sen. Dianne Feinstein ruled out running for governor in the Oct. 7 recall election, giving a boost to Gov. Gray Davis and frustrating some California Democrats, who wanted a replacement candidate on the ballot.

“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,” Feinstein said in a statement.

“I deeply believe the recall is a terrible mistake and will bring to the depth and breadth of California instability and uncertainty, which will be detrimental to our economic recovery and decision-making,” she said, adding that Davis should be allowed to finish the second term he won in November.

Several Democrats had publicly urged Feinstein to run, saying the party needed a fallback position in case Davis lost his job. Her decision left them to search for a new candidate days before Saturday’s candidate filing deadline.

Feinstein tops opinion polls as the state’s most popular politician, and many analysts believed that if she ran, Davis’ chances of survival would diminish.

Her decision came a day after a strong endorsement for Davis from the AFL-CIO. Both developments were key victories for the governor, whose support from fellow party members had appeared to be weakening.

“I’m very pleased with Sen. Feinstein’s announcement,” Davis said on San Francisco radio station KGO-AM.

“To the extent that Democrats get in the race, it makes it look like a normal election, and legitimates what is really an effort by the right wing to steal back an election they couldn’t win last November,” he said. “I think at the end of the day people will realize that the party is better served rallying around its sitting governor.”

Some party members still thought otherwise.

“I want to back the strongest candidate and it’s important that we coalesce around one, and now I’m appealing to the leaders, the folks whose pay grade is one or two notches up from mine, to figure out who our strongest candidate is and lead us in coalescing behind that candidate,” said Rep. Brad Sherman, D-Sherman Oaks, who had supported a Feinstein candidacy.

Shortly after Feinstein announced she would not run, Arianna Huffington held a news conference in Los Angeles to declare that she was getting into the race.

“Today I am announcing that I’m running for governor of the great state of California,” said the political commentator, an independent who is the ex-wife of former Republican Congressman Michael Huffington. “Those are 16 words I never thought I could hear myself say. I’m not, to say the least, a conventional candidate. But these are not conventional times. And if we keep electing the same kind of politicians who got us into the same kind of mess funded by the same kind of special interests, we’ll never get out of this mess.”

Feinstein has served in the Senate since 1992, two years after narrowly losing the gubernatorial election to Republican Pete Wilson. She defeated a recall attempt when she was mayor of San Francisco in 1983.

Her popularity, her desire for the state’s top job — and a frosty relationship with Davis stemming from their rivalry in the 1992 Senate primary — were the main reasons several Democrats publicly urged her to run.

She said she was flattered by those who had urged her to put her name on the ballot, and did not comment on whether Democrats should field a candidate for governor in case voters decide to oust Davis.