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SAN FRANCISCO -- Mayor Gavin Newsom formally announced his candidacy for California governor on Tuesday, offering himself as an heir to the same groundswell for generational change that helped send President Barack Obama to the White House.

Entering a race that could see him competing against men 15 and 30 years his senior, the 41-year-old Democrat pointedly used YouTube and the social networking sites Twitter and Facebook to disclose that he would seek his party's nomination to succeed Gov. Arnold Schwarzenegger.

The move mirrors Obama's early efforts as a candidate to identify and mobilize supporters through the Internet. But Newsom, who campaigned for Hillary Rodham Clinton in the presidential primary, described it as emblematic of the "intuitive" comfort with technology, transparency and consensus-building he says he shares with Obama.

"There will be legitimate questions nationally -- is change an affectation of the personality of Barack Obama and is it exclusive to Washington, D.C. and the occupant of the White House? Or is that change, that generational mind-set, going to take shape across the rest of the nation, starting with the most populous state?" he said in an interview with The Associated Press. "We'll see."

In next year's Democratic primary, Newsom could face Attorney General Jerry Brown, who at age 71 is considering again seeking the office he held from 1975 to 1983, and Lt. Gov. John Garamendi, 64. Other Democrats mentioned as possible contenders include Los Angeles Mayor Antonio Villaraigosa, 56, and U.S. Sen. Dianne Feinstein, 75.

Newsom, who is a little more than a year into his second term as mayor of California's fourth-largest city, already has a level of name recognition that belies his office and experience. He made international headlines in 2004 when he unilaterally directed city agencies to issue marriage licenses to same-sex couples, a monthlong experiment in civic disobedience ultimately halted by the courts.

While his actions five years ago made him a hometown hero, political observers predicted they could hurt him if he chose to pursue statewide or national office. That sentiment was cemented during the contentious campaign over a constitutional amendment to ban same-sex marriage in California last year, when the backers of the ultimately successful measure presented an unflattering portrait of Newsom in one of their ads.

"He is young, telegenic and energetic, but his weaknesses are he is very closely associated with far liberal-left issues, and whether or not that will translate into popularity statewide is the big question," said Barbara O'Connor, director of the Institute for the Study of Politics and Media at Sacramento State University.

Newsom said that to broaden his appeal beyond the San Francisco Bay area, he plans to highlight his background as a successful businessman -- before becoming mayor, he founded a wine store that he parlayed into a string of restaurants -- and as a politician who has been fiscally responsible. For several months, he has been crisscrossing the state and meeting with voters in markedly less liberal areas such as Stockton and San Diego.

"I'm socially progressive, no doubt about that," he said. "People know I will fight for the things I believe in. But they may not know that other side."

His gubernatorial campaign will also promote some of the programs he has spearheaded as mayor, including one that made health care available to uninsured San Francisco residents, a universal preschool initiative, offering solar energy subsidies for homeowners and creating long-term housing for homeless people.

"California is a much wealthier state than San Francisco is a wealthy city, so I don't buy the arguments that it's an ungovernable state," he said.

The most recent statewide poll, released last month, showed Feinstein leading among the possible Democratic candidates with 38 percent and Newsom running a distant fourth, with 10 percent. Without Feinstein in the race, Brown led with 26 percent and Newsom rose to third-place, with 16 percent.

Bill Carrick, a Democratic strategist who works with Feinstein and managed Phil Angelides' 2006 gubernatorial campaign against Schwarzenegger, said Newsom's fresh face message could have appeal with voters frustrated over the state's financial morass. But it is just as likely that Brown's voice of experience will resonate with an electorate that now has a professional actor as its governor, Carrick said.

"You can never underestimate the value of being new in California. We have a culture that operates around the new and different and the cutting edge, so being there is always a strong position," he said. "But on the other hand, we have elected a lot of meat and potatoes. For every Arnold Schwarzenegger, there is a Gray Davis or a Pete Wilson."

In deference to Feinstein, who like Newsom got her start in politics as a San Francisco supervisor-turned-mayor, Newsom said he would drop out of the governor's race if she got into it -- but only if Feinstein makes her move soon.

"I think she is still maintaining an interest and she certainly has the right at any time. But I'm not in a position to wait for that decision to be made and I've made that clear to the senator," he said.

Along with his close tie to the same-sex marriage issue, Newsom has another piece of possible political baggage that could be used against him. In January 2007, he was forced to reveal publicly he had an affair with the wife of his mayoral campaign manager and a drinking problem for which he sought treatment.

The disclosures did not impede him from being overwhelmingly re-elected later that year. Last summer, he married actress Jennifer Siebel, who is now four months pregnant with the couple's first child.

"This is the right time in every respect," Newsom said of his candidacy. "I think the experience is there, I think the perspective is there, I think the record is there. The time couldn't be better."