After last night’s GOP presidential debate, speculation is growing that Mayor Bloomberg is running for president, a prospect that is as incredible in 2007 as his initial run for mayor was in 2000.

What is the scenario that would lead to such a campaign?

Aides suggest that if the candidates of the two major parties tilt to “extremes,” the mayor would enter the fray as a “centrist” alternative. It may come as a shock to the mayor that in much of America, he is not perceived as a centrist. He has clearly earned his stripes as a liberal.

But that aside, who are the radical candidates from which the mayor would save us? Senator McCain? Rudy Giuliani?

Mr. Bloomberg would look like an awful ingrate should he end up running against his predecessor who was so instrumental in his 2001 victory. Perhaps Mitt Romney, stripped of his Massachusetts moderation, might look like fair game. Or maybe if Fred Thompson leaves his ersatz post as Manhattan District Attorney on television, he might qualify as a Republican “extremist.”

As the Democrats scurry to the left for primary season, the mayor may find that Senators Clinton, Obama, and Edwards might qualify as extremists, even though his own positions on gun control, abortion, and gay rights mirror theirs. I don’t recall the mayor leading a charge to find a better candidate to replace Ms. Clinton as New York’s junior senator when she was up for re-election last year.

Now it is possible that other candidates would appear from either left field or right field. But I suspect that the two major party candidates will come from among the aforementioned names.

The prospect of a Bloomberg third party run is greatly facilitated by the accelerated primary schedule that the states are competing with each other to implement: We should know precisely who the Democratic and Republican presidential candidates are by February 5, 2008, in a campaign destined to drag on for an additional 10 months.

This gives the mayor plenty of time to jump in, and he certainly has the resources to get on the ballots of all 50 states as an independent candidate. Should he do so, the major parties might just begin to question the wisdom of the hyper-accelerated and compressed primary schedule that gives a third party outsider the window to mount a credible effort. Make no mistake about it, if Mr. Bloomberg jumps in, he will make Ross Perot’s 1992 effort look like a campaign for high school class president.

Should Mayor Bloomberg decide to run, what will it mean for New York?

First, there will be a huge cry for the mayor to resign. The mayor was roundly criticized for heading out of town in the aftermath of the tragic Bronx fire recently, an event he hardly could have influenced after the fact. Certainly, over the course of the many months of the campaign, there will be a slew of incidents that demand the mayor’s personal attention. It’s tough to race to the scene of a fire or other tragedy, or get to the hospital to console the family of a wounded police officer or firefighter when you are making a campaign stop in California.

But this will not deter the mayor. I suspect that he will resist the call to resign, confident that he can “tough out” the criticism.

The last thing the mayor would want to see is public advocate, Betsy Gotbaum, moving into Gracie Mansion, albeit for a brief period. Ms. Gotbaum has been a leading critic of the mayor’s school reforms, and a general thorn in his side. While she is not on many short lists as a probable candidate under normal circumstances, as an instant incumbent, she may surprise us. She has proven herself in two citywide elections, and could pull off a win in a crowded field.

The real question is, though, whether or not Mr. Bloomberg can win an independent bid for president?

Probably not. And assuming he loses, which party does he hurt more, the Republicans or the Democrats?

Recently, the United Federation of Teachers entered into a surprise détente with the mayor and Chancellor Klein, one that was more advantageous to the mayor than to the union. This came at the precise moment when it appeared that the education issue could well become to Mr. Bloomberg what the Swift Boat campaign was to Senator Kerry.

Knowing that the UFT is a major supporter of Senator Clinton, why should they suddenly change course and be helpful to the mayor’s education reform, even as he nudges closer to possibly running against the union’s friend?

Could it be that those around Mrs. Clinton see a Bloomberg third party candidacy as somehow helpful to her in the same the way Ross Perot is thought to have helped President Clinton in 1992? With a Bloomberg candidacy as a real possibility, the theories and plots are sure to increase — by the billions.

awolf@nysun.com