If Mayor Bloomberg saw the e-mail come over yesterday from Mark Penn, it had to have hit him in the gut. Mr. Penn is the pollster whose firm helped Mr. Bloomberg win the mayoralty. The Bloomberg re-election campaign paid the firm of Penn, Schoen & Berland at least $4.2 million, according to our calculations from government campaign finance records. Now Mr. Penn’s e-mails carry “Hillary for President” letterhead, and he holds the title “chief strategist and pollster” of the Hillary Clinton for President Exploratory Committee.

Mrs. Clinton’s cutesy announcement line — “I’m in, and I’m in to win,” was described by John Podhoretz in the New York Post as “the best political sound bite in years.” The mayor has to realize, though, that Mrs. Clinton’s negatives aren’t just the concerns about whether she can win a general election, but the feeling that she doesn’t stand for anything other than her own ambition. A sound bite that’s not about America, but about herself, and not about securing anything of substance for Americans or the world, but about winning an election, only underscores that impression.

What a contrast with the self-effacing mayor, who can console himself that at least Mrs. Clinton will have to spend the next year hitting up people for money. No matter how many big-bucks speeches Bill Clinton gives to Japanese and Arab businessmen, no matter how many books Hillary signs and sells, the Clintons aren’t going to be worth anywhere near the $20 billion that Mr. Bloomberg is worth. That brings with it certain advantages. Mr. Bloomberg doesn’t have to spend the next year raising money, so he can decide whether to run much later than an ordinary candidate. He can wait it out till next year, once the campaign is more fully formed, and then spend enough money, quickly enough, to get on the ballot and make sure people know who he is, what he stands for, what he has accomplished.

In the meantime, the mayor will keep Mrs. Clinton and the other Democrats on the defensive as much as possible. Mr. Bloomberg chose Mrs. Clinton’s announcement weekend to make a big splash with the release of a report on how to keep New York competitive in the world financial market. Among the recommendations are a cap on punitive damages in lawsuits and an increase in H1B visas for skilled immigrant workers. The report is backed by Mrs. Clinton’s rival — er, colleague — Democratic senator from New York, Charles Schumer. We tip our hat to Mr. Schumer for joining Mr. Bloomberg on this one, and we’ll eat our hat if Mrs. Clinton adopts tort reform as part of her Democratic primary campaign agenda. Senator Dodd, a Democrat who represents Aetna, we mean, Connecticut, might go for it, but he’s vulnerable as a presidential candidate on other issues, such as his soft line on Daniel Ortega.

Still, one has to hand it to Mrs. Clinton — she can move to the center, or to the right, when she wants to. That was a pretty smart move, reacting to President Bush’s proposed surge of troops in Iraq by calling for more troops in Afghanistan. At least no one will mistake her for an isolationist. And how about that December press conference she had with Mr. Bloomberg’s friend Senator Lieberman, calling on parents to make sure that children play “age-appropriate video games,” and praising retailers for not selling “Mature” rated games to children younger than 17 without their parents’ permission?

If Senator McCain is the Republican nominee, or if Mayor Giuliani is, Mr. Bloomberg might decide to stay out. If Mrs. Clinton runs a centrist campaign on the issues, Mr. Bloomberg might also decide to stay out, figuring that she is going to get the votes of his base in New York, California, Massachusetts, New Jersey, and Florida.

But if the Democrats nominate a class-warrior trial lawyer like John Edwards, or a guy like Senator Obama or Senator Biden who has never run anything bigger than his Senate office, maybe Mr. Bloomberg will get in, figuring the campaign might actually be winnable Even if Mrs. Clinton runs a polarizing, hard-left campaign, Mr. Bloomberg might get in. Bill Richardson? Mayor Bloomberg probably figures that as energy secretary, the guy couldn’t even run a security investigation at Los Alamos. If the Republicans pick a hard-liner on social issues — a Senator Brownback, say — there would definitely be an opening for a Bloomberg type, a candidate who is tough on security and fiscally responsible but who favors keeping government out of the bedroom.

Governor Romney of Massachusetts, Michigan, and Bain Capital may be the only candidate whose personal wealth even remotely approaches Mr. Bloomberg ‘s. But unlike Mr. Bloomberg, Mr. Romney never won reelection. Mr. Romney never even tried. Every day, every candidate, every dip or rise in the polls and the press, is a new equation in Mr. Bloomberg’s political calculus. What we and many New Yorkers have learned in watching him these five years is not to underestimate him, nor to count him out prematurely.