washington -- New York City Mayor Michael R. Bloomberg quit the Republican Party on Tuesday, fueling speculation that the billionaire will shake up the presidential race by running as an independent.
Bloomberg has been moving to raise his national profile for months, drawing attention to his support for gun control, stem cell research and steps to stop global warming. Term limits bar him from seeking reelection as mayor.
A former Democrat, he says his decision to sever all party ties "brings my affiliation into alignment with how I have led" New York.
"Any successful elected executive knows that real results are more important than partisan battles and that good ideas should take precedence over rigid adherence to any particular political ideology," he said in a statement Tuesday night.
Hours before his announcement, Bloomberg told reporters in Los Angeles that he had "no plans to announce a candidacy" for president. But his advisors have long encouraged talk of a Bloomberg run for the White House.
And his vast personal fortune -- more than enough to match spending by either major party's nominee -- has forced candidates already in the race to treat Bloomberg as a potentially serious threat.
Still, Bloomberg could face enormous obstacles, including trouble getting his name on the ballot in some states. With sharply contested races under way for the Republican and Democratic nominations, it is anybody's guess how his candidacy could tilt the general election.
"I could draw a scenario where Bloomberg could be extraordinarily helpful to the Republican, or extraordinarily helpful to the Democrat, depending on how he positions himself," said Republican pollster Tony Fabrizio.
In New York, Bloomberg has often stressed his record on crime-fighting and the economy, traditional Republican themes, along with school reform, the environment and other issues more closely associated with Democrats.
Bloomberg, 65, who built his wealth in financial data and media, was a longtime Democrat before becoming a Republican in 2000 as he launched his first campaign for mayor of New York.
On a California tour this week, he often echoed favorite topics of the Democratic presidential candidates. At Google headquarters in the Silicon Valley on Monday, he said America's "reputation has been hurt very badly in the last few years" and denounced what he called the administration's "go-it-alone mentality."
In Century City on Tuesday, Bloomberg said presidential candidates should look to places like New York City and California as models of how to focus on what matters.
Speaking at a USC conference, "Ceasefire! Bridging the Political Divide," he pointed to climate change and stem cell research as areas where cities and states had stepped in to make up for federal inaction.
"When people seek the presidency, hopefully they will address these issues rather than issues that are of importance to a small number of people," he said.
Foreshadowing his party switch hours later, Bloomberg said fighting crime and pollution had "nothing to do with whether you are a Republican or a Democrat."
Joining him at the conference was Gov. Arnold Schwarzenegger, who coasted to reelection last year only after dumping his sharply partisan Republican agenda of the year before. Asked about Bloomberg's potential White House run, Schwarzenegger said: "I think he would make an excellent candidate. It's all about fixing problems and creating a great vision for the future."
On the cover of Time magazine's current issue, Bloomberg and Schwarzenegger appear together under a headline that says: "Who Needs Washington?"
Schwarzenegger has branded his own style of governing as "post-partisanship," but reaffirmed his Republican identity on Tuesday.
"Some people say, 'Arnold, haven't you maybe sold out a little bit here and became an independent?' No, I am still a proud Republican, and I support the guiding principles of the Republican Party: lower taxes, a strong defense, free market, and the belief in the power of the individual."
If Bloomberg decides to run as an independent, history suggests a tough climb to the presidency.
Polls show voters are overwhelmingly dissatisfied with the country's direction, the same condition that propelled the independent candidacies of John Anderson in 1980 and Ross Perot in 1992. But Anderson and Perot each lost by wide margins.
"The climate is there," said Tim Hibbitts, a nonpartisan pollster in Oregon. "The question is whether Bloomberg or somebody else can strike the spark that will set things off."
Bloomberg's prospects also depend heavily upon who ultimately wins the Democratic and Republican nominations.
His candidacy would probably be premised upon one or both parties putting up "badly flawed or badly damaged candidates," said Charlie Cook, publisher of the Cook Political Report, a nonpartisan newsletter.
"This guy has no interest in running and losing," Cook said.
Finnegan reported from Washington, Halper from Los Angeles. Times staff writer Josh Getlin in New York also contributed to this report.