A little past 6 p.m. on the evening of June 19, Michael Bloomberg’s press office sent out the following statement:

“I have filed papers with the New York City Board of Elections to change my status as a voter and register as unaffiliated with any political party.”

And just like that, all the theories about the Mayor’s independent candidacy for President in 2008 became not so theoretical.

Yes, that innocent-sounding statement was followed by a ritualistic denial by the Mayor about how his plans for the future hadn’t changed.

But what does that mean?

No elected official, it’s fair to presume, is immune to the lures of running for higher office; when the press, the public and a coterie of politicians are egging him on, resistance is futile.

(And honestly, it’s not going to be any easier for the New York press to restrain itself about the increasingly real prospect of a three-way race between Hillary Clinton, Mike Bloomberg and Rudy Giuliani.)

Could it be a coincidence that June 15 was the day Deputy Mayor Ed Skyler showed up, according to a source at the board, to meet with the chairman of the New York City Board of Elections to register the change—the same day the Mayor appeared on the cover of Time magazine, leaning up against a smiling Governor Arnold Schwarzenegger, over the legend “The New Action Heroes”? (The announcement of the switch was made four days later, shortly after it was reported on the politicker.com blog on this newspaper's web site.)

Or that he’s switching his affiliation even as he maintains a packed out-of-state travel schedule that has, recently, included stops in Oklahoma, Texas, California and (ahem) New Hampshire?

Could the Mayor’s decision to abandon his marriage of convenience with the Republican Party—he enrolled, as New York voters will recall, as an easy and relatively cheap means of gaining access to the ballot for his Mayoral run—possibly represent anything but the first trotting step in his much-talked-about run for President as a self-financed independent?

The answer, from some of the people who know him best, is maybe.

“I think it’s important for him to be on the national stage regardless of whether he runs,” said Barnard College professor Esther Fuchs, who served as a special advisor to the Mayor in his first term. “I think whether he runs or not, he needs to do everything to make himself a relevant figure in the national political debate. It makes sense for him to do this because he will be taken most seriously this way on issues that are important to New York City—and that’s really his goal.”

Or his short-term goal.

“This is another trial balloon,” said Hank Sheinkopf, a Democratic consultant who worked on the Mayoral campaign of Mark Green in 2001. “If it doesn’t explode, it will empower Bloomberg and people who would support a Bloomberg campaign. It will certainly fuel speculation over the summer and this may end up resulting in a ‘Draft Mike Bloomberg’ campaign.”

And this, from former New York City Mayor Ed Koch, who endorsed Mr. Bloomberg’s bid for re-election and, handily, has just written a book entitled Buzz: How to Create It and Win with It.

“I believe he is running,” Mr. Koch said, “but that he is not running today. But he doesn’t need to make a total, final decision between now and the end of the year. The other candidates have to start so early to raise money. He doesn’t have to do that. I heard that he is willing to spend up to $800 million of his money.”

Certainly, Mr. Bloomberg’s declaration of his partisan independence hasn’t lessened his usefulness as a political ally, as New York Republicans—who might normally have taken somewhat unkindly to a local leader bolting the party that supported himimmediately made clear.

“Mayor Bloomberg has built a remarkable record in office and has delivered results,” read a statement released by the office of New York State Senate Majority Leader Joe Bruno, “because of his tremendous ability to work with people of all political parties and persuasions and regardless of his own political affiliation.”

The suddenly self-perpetuating speculation about his Presidential intentions is certainly good for the Mayor whether he runs or not. It gets him a national audience for his issue advocacy, and wards off lame-duck status at home.

It also creates leverage with anyone who’d prefer for him to stay out of the Presidential race.

And if the public can seriously speculate about the entry into the Democratic primary of a flawed campaigner like Al Gore, and if the Republican primary field can be turned on its head by Fred Thompson, a lightly accomplished Senator who can act, how can anyone dismiss the possibility of an independent Bloomberg candidacy?

Because here’s the thing: He’s popular in New York, he has room to make a positive impression elsewhere and—this is the key—he has billions of dollars to sell himself to the country.

And as laughable as it may seem to say so, his two successful Mayoral campaigns in New York may end up providing useful precedent. Yes, the five boroughs bear little resemblance, demographic or otherwise, to, say, Iowa or New Hampshire. But the city is nonetheless once-foreign political territory for Mr. Bloomberg, a politically incorrect billionaire businessman with a funny Boston accent.

He flooded the zone, spending tens of millions of dollars to conduct the most thorough polling ever compiled for a municipal election, to advertise in normally neglected niches like ethnic newspapers and radio stations, and to blanket the airwaves with an advertising onslaught the likes of which even New York City had never seen.

It worked. In 2001, just weeks after Sept. 11, he was elected with the help of Rudy Giuliani’s support, when Rudy Giuliani’s support mattered most. In 2005, he was re-elected without help from anyone, compiling large margins of victory among most measurable sub-categories of voters.

Yes, the scale of a national race is incomparably larger. Yes, to become President, he’d have to figure out how to win most states outright to collect their electoral votes—not just win a lot of votes in a lot of states, like wacky Ross Perot back in 1992.

And yes, as he has (modestly?) pointed out, central casting doesn’t generally assign the role of Winning Presidential Candidate to short, divorced Jews.

The Mayor’s aides, who last year made a show of fantasizing about a Bloomberg bid for the White House, are now sticking with the line that the Mayor’s registration as an independent is a practical political gesture that has nothing to do with 2008.

“He has said every which way, in the past future and imperfect tense, that he is not running for President,” said spokesman Stu Loeser. “He is not running and he will not run for President. He has been asked the question every way and he has answered it every way.”

Pressed for something more, Mr. Loeser offered this: “He is not running for President. What he has acknowledged, in fact he has emphasized, is that a heightened profile helps us, helps him push his agenda in Albany and Washington.”

Certainly, this all seems very much in keeping with the public statements the Mayor has been making for a while now.

“I’ve said it a thousand times,” Mr. Bloomberg said several weeks ago at a press conference in Queens, in the course of batting away the latest in a string of 2008-related questions from reporters. “What else do you need?”

Well …. Where do we begin?

—additional reporting by Jason Horowitz and Azi Paybarah