Mayor Bloomberg’s decision to quit the Republican Party is being interpreted as a significant step in the direction of declaring an independent run for the White House.

Mr. Bloomberg sent out a statement last night saying that he had filed papers with the New York City Board of Elections to change his voter registration status so that he is no long affiliated with any political party.

While Mr. Bloomberg still insists that he is not running and that he will become a full-time philanthropist when his term ends, the move seems to validate the presidential speculation that has followed him as he’s traveled the country, rolled out national policy agendas, and been featured on the covers of national magazines.

“He’s laying the foundation,” said a national political strategist who worked on the Gore and Kerry presidential campaigns, Robert Shrum. “It will no longer be dismissed as just Kevin Sheekey and Mitchell Moss talking about it,” he added, referring to Mr. Bloomberg’s chief political strategist and one of his advisers.

Mr. Bloomberg’s statement said his “plans for the future haven’t changed,” and that being unaffiliated only “brings my affiliation into alignment with how I have led and will continue to lead our city.”

An independent candidate for president in 1980, John Anderson, told The New York Sun that Mr. Bloomberg’s change in party affiliation was a positive sign for a possible run.

“I have been looking hopefully over the horizon hoping an independent candidate might emerge,” Mr. Anderson, who had served as a congressman from Illinois before winning about 7% of the national vote in his independent bid for the White House, said.

Mr. Anderson said Mr. Bloomberg has the ingredients of a strong independent candidate. “He has a remarkable record in New York City — a record of genuine accomplishment.”

Switching parties is not new for the billionaire mayor. He was a lifelong Democrat who became a Republican to run for office in 2001.
Douglas Bailey, a former Republican political consultant who co-founded the Hotline political newsletter and now is CEO of Unity08, which aims to nominate a third-party ticket in 2008, said that while he did not want to read into Mr. Bloomberg’s plans the decision to become an Independent was a “very encouraging sign.”

“I just assume there is some reason why he is doing it and if it’s to prepare for a candidacy for president I think that is to the good of the country,” Mr. Bailey said.

An independent ticket would be in direct competition with the Democratic nominee, who many presume will be Senator Clinton, and the Republican nominee, who could very well be Mr. Bloomberg’s predecessor at City Hall, Mayor Giuliani. The Clinton and Giuliani campaigns both declined to comment on Mr. Bloomberg’s new party affiliation.

Some political analysts said that not being affiliated with a party in New York could make it easier for Mr. Bloomberg to get on the ballot as an independent in certain states if he does run.

The editor of Ballot Access News, Richard Winger, told The New York Sun that Mr. Bloomberg will not face any legal problems as an independent and noted that he will be able to bypass primaries nationwide. He also said the change in party affiliation would make it easier for Mr. Bloomberg to run on a ticket with a Republican or Democrat of his choosing if he goes with Unity08. The organization has said it will not nominate two members of the same party.

The move comes months before Mr. Bloomberg would likely declare a candidacy and well before any presidential deadlines. He can also point to the fact that he has essentially become a poster child for a national independent movement, chastising Washington at every turn for its partisan gridlock.

In recent weeks, Mr. Bloomberg has been politically linked to Senator Hagel, a Republican of Nebraska, who suggested on CBS’s “Face the Nation” last month that the two could team up for a ticket. Also mentioned as a possible Bloomberg running mate is David Boren, who served as a Democrat as governor of Oklahoma and senator from Oklahoma.

The announcement came a day after Mr. Bloomberg belittled the state of the 2008 presidential race during an appearance at the California headquarters of Google, a regular stop for presidential candidates.

While he said he had no plans to run for president, he also refused to completely rule out it out. And, he said the candidates had “pandered” during the televised debates and that they were not offering real solutions for the pressing issues.

When asked yesterday whether Senators Clinton and Schumer have contributed to the partisan acrimony in Washington that he has been criticizing, Mr. Bloomberg had only positive things to say.

“I think Senators Clinton and Schumer have been great senators,” the mayor said. “Whenever I need something in Washington they are there.”

The head of the New York state Independence Party, Frank Morano, said he was “tickled pink” by the news the Mr. Bloomberg is no longer a Republican, saying it was a historic day for the independent movement. “I’m still just on such a euphoric high. I haven’t been able to sit down,” he said. The Independence Party is a legacy of Ross Perot’s third-party presidential candidacies.

In March, the Pew Research Center on the People & the Press reported that 34% of Americans identified themselves as independents in February, up from 30% from February 2006.

Meanwhile, Mr. Bloomberg and Governor Schwarzenegger launched into something of a political comedy act yesterday when talking to reporters after a conference on ending partisanship in California.

The gathering of journalists and public officials was fertile ground for discussion of a possible independent bid by Mr. Bloomberg. In response to a question, Mr. Schwarzenegger, a Republican, offered his most full-throated endorsement yet of a Bloomberg campaign.

“I think he would make an excellent candidate, yes,” the governor said.

“It’s all about fixing problems and creating a great vision for the future. I’ve never seen someone’s that quick with the action.”

Mr. Bloomberg brushed aside the talk. “I have no plans to announce a candidacy because I plan to be mayor for the next 926 days,” he said.

Still, he was not above indulging a hypothetical question about running with Mr. Schwarzenegger, an Austrian-born former bodybuilder. “There would be a fight to see who would be the presidential candidate and who would be the vice presidential candidate. He would want to arm wrestle for the top spot. I would want to check the Constitution,” the mayor joked, referring to the requirement that presidents be citizens at birth.

An adviser to Senator Lieberman — who became an independent after losing the Democratic primary for his Connecticut senate seat — said that move to become unaffiliated with a political party was a smart one.

“He recognizes that his juice is getting stronger. He has an opportunity regardless of whether he decides to run for president to use his influence to advance his agenda,” said the adviser, Daniel Gerstein.

The Republican National Party said only that it was “sorry to hear” of Mr. Bloomberg’s decision and the Republican majority leader in the state senate, Joseph Bruno, said the mayor has provided “strong leadership” and that he has built a “remarkable record.”