In August 1997, Democratic mayoral hopeful Ruth Messinger filmed a television commercial that portrayed a class of public school students being taught in a bathroom, an attempt to highlight school overcrowding. The message was that Mayor Giuliani, who trimmed the budget of the school system, was responsible for this outrage.

Unfortunately for Ms. Messinger, the commercial was totally staged, filmed in a rented private school, portraying a condition that was totally atypical of the reality of the public school system. No one was more outraged than Rudolph Crew, who was then schools chancellor. He charged Ms. Messinger with “sordid duplicity” and that she “acted in very, very, very poor taste” and engaged in “gross misrepresentation” by depicting children “routinely being seated in urinals.”

That was, at least in my memory, the first and last time, until this week, that a chancellor involved himself so overtly in partisan politics. In 1997, chancellors were selected by the old Board of Education, though the mayor had a role in the selection process. Every mayor since Mayor Koch aggressively used his two appointees and all of their influence to ensure that his interests were protected.

Mayor Giuliani literally drove the hapless Ramon Cortines out of town after he couldn’t produce a credible figure for the number of central office employees. When the Board of Education informally selected Daniel Domenech, a superintendent from Suffolk County, to replace Mr. Cortines, the mayor called one of the board members, Staten Island representative Jerry Cammarata, in for a little heart-to-heart chat.

Mr. Cammarata was persuaded to change his vote, and Mr. Crew was chosen as the new chancellor. It wasn’t that the mayor had any particular relationship with Mr. Crew. He didn’t. But Mr. Giuliani felt it was important that the person who was selected to lead the schools be his choice, even if there was no special bond.

Mr. Crew was able to create a focus on assessment and instruction, formed the Chancellor’s District, which made remarkable gains in turning around the worst schools, and removed the patronage powers of the local school boards through a reform bill passed in a special session of the legislature at the end of 1996.

So by August 1997, when the Messinger commercial ran, Mr. Crew was considered golden and was actually touted by some as a possible future mayoral hopeful himself. That’s why Ms. Messinger was so upset with Mr. Crew’s response to her commercial. “What the chancellor did,” she fumed, “that was just appalling…to inject himself into the middle of this campaign. The chancellor’s job is to educate children, not to be out there campaigning for the mayor.”

It will be interesting to see if and how the response around town to Schools Chancellor Joel Klein’s comments on two of the mayor’s opponents, as broadcast on New York 1’s “Inside City Hall” Monday evening. After all, the mayor asked to assume responsibility for the schools and asked to be judged by his performance.

With a recent poll indicating that 68% of New Yorkers give Mr. Bloomberg a failing grade on education, Mr. Klein may have reason to be a bit testy. But is he helping the mayor by charging politics is behind the criticism that Mr. Bloomberg himself said he welcomed?

Mr. Klein said: “This is the political season. And, you know, the other night you had Anthony Weiner on here. He doesn’t know what he’s talking about but he’s going on and on…So now what you’re seeing…is you’ve got a race for the mayor and people are going to just, you know, whack away, because that’s the way it goes. They don’t care what the facts are.”

Mr. Weiner did issue a number of positions on education, which could lead to a spirited debate that Mr. Bloomberg could engage in. Whether this is a logical role for Mr. Klein is less clear.

The chancellor’s harshest remarks were reserved for Fernando Ferrer, the Democratic front-runner, even though he conceded, “Mr. Ferrer, as far as I can tell, hasn’t said anything about education, but my sense is that what’s going to happen now is people are going to try to politicize an issue, that, you know, Mr. Ferrer was in office for many, many years. Right? What did he do? What happened to those kids then? You know, when he was borough president, right, what was going on in this city?”

So let the debate begin.