What is the biggest mistake so far in the mayoral campaign? Is it Fernando Ferrer’s flip-flop flub on the Diallo case? Or is it the idea of the “nonaggression” pact between mayoral hopefuls C. Virginia Fields and Mr. Ferrer?

This is an election between four people who seek the right to challenge Mayor Bloomberg as the Democratic standard bearer. If any of the four don’t believe that they are the best in the field, why are they running? This is not ballet. Voters want candidates to forcefully make their case.

Ms. Fields’s campaign manager is Joseph Mercurio, a well-known political pro who has fans – and customers – in both parties. Last week he offered his analysis of the Ferrer flap, spinning it Ms. Fields’s way. That’s his job, and I don’t know too many knowledgeable political types who would disagree with much of what he had to say, although they may differ on which candidates benefit.

Here are some of Mr. Mercurio’s comments: “Currently, Ferrer has an advantage only in name recognition. His vote is soft and is easily moved to Fields by events. Both Ferrer and Fields are both leading Mayor Bloomberg. The difference in lead, a result of name recognition, will fade. Voters will move away from Ferrer to undecided, and then they will move to Fields because of Ferrer’s flip-flops.”

Does this constitute an attack on Mr. Ferrer? Apparently, that’s what some of the former Bronx borough president’s aides are suggesting. This isn’t an attack, it’s an informed opinion.

Perhaps the Ferrer minions are taking their cue directly from the notoriously thin-skinned Mr. Ferrer. Or perhaps the guidance comes from strategy laid out by campaign chief Roberto Ramirez, a reprise of tactics from four years ago. The hope is that by characterizing a mild rebuke or even an analysis as an unfair “attack,” that will make it so in the mind of the public. In 2001, that was a part of the game plan against Mark Green. If Mr. Green looked at Mr. Ferrer cross-eyed, he was accused of an attack. After a while, Mr. Green became tentative and less effective in debates, which may have contributed to his decline from clear front-runner to a second-place finish in the first primary and finally beating Mr. Ferrer by an eyelash in the runoff.

And, of course, once Mr. Green narrowly won the runoff, Mr. Ferrer, still offended by campaign fliers that reproduced a New York Post cartoon of him kissing the Reverend Al Sharpton’s derriere, proved he can hold a grudge when he refused to endorse Mr. Green despite the entreaties of top Democrats right up to President Clinton.

As the front-runner, Mr. Ferrer benefits from a campaign played by the Marquis of Queensbury rules. Why his opponents go along is beyond me. Mr. Ferrer brings a record of over 14 years as Bronx president, and a stint in the City Council prior to that. These were not good years for the people of the city’s most troubled borough. His record deserves review.

In fact, all of the hopefuls have records, and those records should frame the discussion. After all, promises are easy to come by, but performance in public office represents the analysis of the good and the bad, the hard facts that constitute a record.

The other thin-skinned candidate in the race is the mayor, who demonstrates this every time someone raises the issue of education.

Similarly, the mayor may dismiss the opponents of the West Side stadium project as against the best interests of the city, but this issue has now reached a “no-win” situation for Mr. Bloomberg. The possibility of a 2010 Super Bowl in New York and the odd-couple linkage of Mayor Giuliani and Mr. Sharpton backing the plan has dramatically increased the likelihood that the stadium project will move forward.

But the mayor still has to answer for his advocacy of the Jets’ initial plan proposing to pay just $100 million for the site. The debate on this issue already has guaranteed that the cash strapped Metropolitan Transportation Authority will receive $620 million more than what Mr. Bloomberg was prepared to accept not all that long ago.

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Mr. Ferrer is unlikely to confront his Democratic opponents in a lunchtime debate at Hunter College tomorrow, and the president of the student government speculates that the former Bronx borough president may be concerned about student reaction to the Diallo issue.

According to Miles Gerety, Mr. Ferrer may be worried about a hostile reaction from black students. Mr. Ferrer has agreed to debate his opponents next month at a forum sponsored by Crain’s, where his remarks on the Diallo case will presumably play better.