When Michael Bloomberg was deciding whether to run for mayor in 2001, winning was the goal but the idea of losing wasn’t particularly scary to him. Mr. Bloomberg viewed the opportunity to emerge as a leading voice for change in the city as worth the risk of losing the election.

As he nears a decision on whether to run for president, though, Mr. Bloomberg is no longer pining to make his opinions about what he considers the most pressing issues of our time relevant to the political discourse — he’s already won a seat at that table. Mr. Bloomberg will only flip the switch on Bloomberg for President if he really believes he can win.

The only way Mr. Bloomberg has any chance of becoming the first independent candidate to win the presidency is if Democrats and Republicans nominate candidates who don’t satisfy and inspire voters. That won’t be clear until early March. Until then, Mr. Bloomberg’s advisers have a green light to gear up for a run while they talk up his appeal and also his willingness to spend perhaps up to $2 billion on a national campaign.

Mr. Bloomberg’s personal mission is to build on his civic accomplishments that can’t possibly be seen all the way to fruition in just two terms as New York City mayor. He’d like to do that as president. But his determination to give away most of his roughly $15 billion fortune will keep his opinion relevant for as long as the cash spigot is open. The question is whether he’ll try for commander in chief or settle down as one of the nation’s chief philanthropists. Serving as mayor — particularly as a mayor who could make a credible run for president — has allowed Mr. Bloomberg to influence a wide range of issues. That effort began a couple of years ago, around the same time whispers of a possible presidential bid first began making the rounds. Mr. Bloomberg’s denials about his national aspirations were as consistent as his team’s behind-the-scenes efforts to make those national aspirations possible.

Mr. Bloomberg’s presidential platform would seek to build on what he has accomplished as mayor by arguing that the current political system is broken and thus prevents government from achieving the common good. Mr. Bloomberg would run on a clear agenda of specific issues that he believes transcend political leanings, partisan bickering or personal bias by having a direct impact on the quality of our lives — as seen in speeches about science and medicine at his alma mater Johns Hopkins, in appearances with independent-minded Governor Schwarzenegger about the environment, in his campaign against guns, and most recently in his focus on bringing the developing world into our world, which we saw in his recent Asian adventure. Mr. Bloomberg sees all this as the basis of an agenda that will somehow stand out in contrast to usual presidential campaign paradigm that often leads candidates to fight decades-old battles in the framework of appealing to a natural political base.

The only chance for Mr. Bloomberg’s message to resonate depends on voters shaking their heads at their options after the front-loaded primary season produces nominees. If the Democratic or Republican candidates have broad appeal and inspire voters, there isn’t much incentive for voters to give Mr. Bloomberg’s results-oriented determination a chance to peel voters them away from their natural instincts.

But then there are the ifs that might make Mr. Bloomberg decide to run: If the candidates are disappointing to a large swath of the electorate, if the economy remains uncertain, if Congress remains dysfunctional, if immigration and other issues remain touchy but mired in the muck. In a nutshell, Mr. Bloomberg will enter the race if voters are truly disappointed with their options and the nominees are forced to appeal to the extreme wings of their parties — thus leaving open a middle ground of frustrated voters.

There’s been a lot of speculation lately about the scenarios that would cause Mr. Bloomberg to throw his hat in the ring. The basic theories hold that he’s hoping for candidates with high “negatives” who are so anathema to a large enough number of voters that an alternative candidate has an opening for success because the other options are so controversial.

The conventional wisdom says Mr. Bloomberg wouldn’t run against Senator McCain because he’s a centrist, Governor Romney because he’s a fellow businessman, or Senator Clinton because they share so many of the same natural base of supporters. But conventional wisdom can’t tell us how voters will feel about any of the nominees once their opponents have finished slicing and dicing them during the next 10 weeks of campaigning.

Name any pair of candidates, and there is a scenario that allows Mr. Bloomberg to conclude he has a decent shot at winning. But decent does not mean likely, and odds are Mr. Bloomberg will sit out the race.

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