To the idea of running for president in 2008, New York Mayor Michael Bloomberg says “No, no and NO.” And, granted, he’d be a long shot if he changed his mind. Still, I hope he keeps his powder dry and his checkbook handy. [IMGCAP(1)]

Right now, there is still a strong possibility that it won’t be necessary for Bloomberg to mount an independent, third-party bid because both major parties have leading candidates who can appeal to the moderate near-majority of American voters.

But incessant demands from the liberal and conservative base constituencies of the two parties could produce a polarized choice by next February, leaving room — indeed, a demand — for a moderate third choice.

In 2006 election exit polls, a full 47 percent of the electorate identified itself as moderate, only 20 percent as liberal and 32 percent as conservative.

Polling since then shows a decided public preference for politicians who are willing to compromise with the opposition to solve problems — and skepticism that the current Congress and administration will do so.

A Pew Research Center poll in January showed that 75 percent of voters believe that the ability to compromise is a positive characteristic in politics and that by 60 percent to 34 percent they prefer politicians who take a mix of liberal and conservative positions.

In the poll, fully 62 percent said they dislike politicians who take liberal positions on nearly all issues, and 57 percent dislike those who are almost always conservative. Less than 40 percent said that Congressional Democrats and President Bush are willing to reach out to the opposition.

The poll indicated that the ideal is a politician who is moderate on issues but also has convictions. That’s Bloomberg, who has reduced crime in New York, improved its economy, expanded affordable housing, pioneered school reform and held the city together.

The billionaire Democrat-turned-Republican was re-elected in 2005 by a margin of 20 points, outstripping the previous records set by Fiorello LaGuardia in 1937 and Rudy Giuliani in 1997.

New York Democrat Meyer Frucher, once a top aide to former Gov. Mario Cuomo, says that Bloomberg, “as a personality, is the antithesis of Giuliani, in that he is calm, collected, professional and has been able to reach out to every sector of the city, whereas Rudy was a polarizer who people felt was insensitive to people of color.”

Of all Bloomberg’s accomplishments, the most impressive to me is his assumption of responsibility for the city’s schools, the hiring of former President Bill Clinton aide Joel Klein as schools chancellor, and his willingness to take on entrenched interests, led by the United Federation of Teachers, to make the interests of children the schools’ top priority.

As Klein put it in a speech in January, he and Bloomberg decided against incrementalism in view of the system’s past failures and wouldn’t accept the idea that endemic failures in society make educating poor children impossible.

“That argument, put forward by many,” Klein said, “serves only to breed low expectations and a culture of excuses.” Klein and Bloomberg instead have tried to foster a climate of accountability.

Test scores and graduation rates have improved, and Bloomberg announced in his State of the City address this year dramatic new moves that will dismantle the bureaucratic supervisory structure and empower all the city’s principals to select their own support system.

In Bloomberg’s first term, he directed more than $200 million away from the education bureaucracy to schools and classrooms, increasing teacher pay by 43 percent and offering bonuses for teachers of math, science and special education and those who mentor other teachers. He’s set a goal of $200 million more for this term.

To the dismay of the union, Bloomberg proposed to end automatic tenure for teachers after their three-year probationary period, requiring them to show improvement in their students’ performance. He’s proposed rating all schools from A to F and making data on school and student performance readily available to parents.

It’s worth noting that, among Democratic candidates for president, only Sen. Barack Obama (D-Ill.) has even remotely challenged teachers unions — and his proposals are strictly experimental — and, among Republicans, none is proposing to increase teacher pay in return for stiffer accountability.

Obama’s main campaign promise is a de-polarized “new politics,” but it remains to be seen whether he can deliver specific proposals capable of attracting bipartisan support.

Democratic frontrunner Sen. Hillary Rodham Clinton (N.Y.) witnessed successful “third way” politics — also known as “triangulation” — in her husband’s administration, but tends to be a polarizing figure for Republicans.

Encouragingly, both Clinton and Obama have resisted left-wing demands for an immediate withdrawal from Iraq, but they have caved to pressure for withdrawal deadlines.

Among Republicans, Giuliani, Sen. John McCain (Ariz.) and former Massachusetts Gov. Mitt Romney all have records of action across party lines and of resisting base pressure, although Romney is rapidly becoming a poster child for acquiescence to conservative pressure.

Bloomberg, while repeatedly ruling out a run in 2008, is the constant subject of rumors that he’s willing to use part of his fortune to finance an independent bid. Sponsors of the online third party effort, Unity 08, also hope that he’ll seek their nomination.

He’s kept the rumors alive by speaking out on national issues such as Iraq and denouncing Democratic withdrawal deadlines, and he campaigned last fall for Sen. Joe Lieberman of Connecticut, now an Independent Democrat.

Bloomberg has a moderate position on immigration, favoring biometric ID cards, more work visas and a path to citizenship for illegal immigrants. And he’s proposing health care reforms emphasizing disease prevention.

Obviously, the historical record of third parties is dismal. Not even ex-President Theodore Roosevelt could win. But, every decade or two, third-party candidacies do serve a purpose. They impel the major parties to take action they might otherwise avoid.

In 2008, all indications are the public wants an end to incessant partisan combat and attention to pressing national problems. If Democrats and Republicans can’t deliver, Bloomberg has shown that he can.