Street, the Democratic nominee, pledged to retain John Timoney as police commissioner, a step that Katz had favored all along.

Katz, the Republican nominee, promised to reduce the wage tax that Philadelphia residents pay to 4 percent or less, a position that Street asserted was fiscally irresponsible.

The remarks were made in a taped debate that will be broadcast at 5 p.m. today on WPVI-TV (Channel 6).

It was the first of two debates on what turned out to be an extraordinary day of mayoral politics, in which it was clear that the candidates differed on several fundamental issues.

Segments of the second debate, held at the Zellerbach Theater on the University of Pennsylvania campus, will be broadcast on mornings this week on public radio station WHYY-FM (90.9).

Until yesterday, Street had tiptoed around the question of whether he would keep Timoney, turning it into a yes-or-no issue that was beginning to dog his campaign.

Also until yesterday, Katz had shied away from a comment he had made in February that he would cut the wage tax from its current 4.61 percent to 4 percent or less over the next four years. He had said only that he wanted to make cuts and would say later how much.

The Timoney question arose in a discussion about crime during the TV debate, which was taped a little after 10:30 a.m. at the Channel 6 studios on City Avenue and was cosponsored by the NAACP.

Katz prodded Street by commenting: "I don't find reappointing John Timoney a distraction to my campaign. I think it's a vital thing for the future of the city to send a message to the guy."

Street, who moments before had been hounding Katz for his unwillingness to take a stand on the wage tax, replied: "John Timoney is somebody who is very near and dear to me."

He said he deserved some of the credit for bringing Timoney to Philadelphia from New York, where the police commissioner had been the No. 2 man in a department that had helped reduce crime by 39 percent between 1992 and 1995.

Still, Street stopped short of saying he would ask Timoney to stay.

Finally, he began to utter the words: "I'll tell you yes or no . . ."

But the moderator, Monica Malpass, a Channel 6 news anchor, cut him off with an unrelated question.

It took Street a few moments to get back in. He looked at Katz and said: "I'll reappoint John Timoney. Does that make you happy?"

A Street adviser said last week that it was not that his candidate disapproved of Timoney, it was that he did not want to commit himself on top city posts until after the election.

Some in politics were reminded of the 1967 mayoral campaign. Republican U.S. Sen. Arlen Specter, then a candidate for mayor, refused to say whether he would appoint Frank L. Rizzo, a popular figure, as police commissioner. Democrat James H.J. Tate said he was all for Rizzo. Tate won the election narrowly.

The wage-tax question was also politically loaded. It carried echoes of the spring Democratic primary, in which Marty Weinberg pledged to reduce the wage tax to 4 percent as a means of trying to keep residents and businesses from fleeing the city for tax reasons.

Street and the other three major candidates - John White Jr., Dwight Evans and Happy Fernandez - criticized Weinberg as irresponsible, even though he had said: "We have no choice. Despite everything that has been accomplished in the last eight years, 150,000 people and many, many businesses have left Philadelphia."

Katz uttered almost identical words at the TV debate yesterday.

Later, at a forum at the Zellerbach sponsored by The Inquirer and the Philadelphia Compact, Katz said he planned to "equalize" the tax rate for residents and for nonresidents who work in the city. The nonresident rate is currently 4.01 percent.

Getting the issue out was important to Street because he had sought to paint Katz as someone who would slash city services and sacrifice the needs of residents for the sake of tax cuts.

Street said a cut to 4 percent would remove $500 million from the city budget over the four years of the next mayor's term.

Street favors the tax-reduction plan in the city's current five-year plan. That calls for the resident rate to be cut to 4.46 percent over four years.

He said: "I want to reduce taxes . . . but if you're talking about taking large hunks out of the budget, somebody has got to tell me what we're going to cut."

Again and again, Street demanded of Katz: "What are you going to cut? What are you going to cut?"

Katz did not take that bait. He said he would announce his tax plan when he was ready, and would say then how he proposed to balance the city's $2.7 billion budget.

But he indicated he did not believe that the revenue loss would be as severe as Street suggested, saying that the cuts might persuade some people not to leave the city - and not to take tax dollars with them.

"We will find the savings that allow us to engage in faster tax reduction," he said.

The debates yesterday were the first in at least a half-dozen that the candidates are expected to engage in over the next four weeks. The election is Nov. 2.

Constitutional Party candidate John McDermott was not included in either event yesterday.

Besides Timoney and taxes, the issue that grabbed the most attention was the city schools.

The mayor does not directly control the city schools, but he appoints the members of the board. City Council has to sign off on the school budget and tax appropriations.

Both major candidates pledged to play a more aggressive role than former mayors had in trying to oversee the schools.

Katz told a panel of citizen questioners at the Zellerbach debate that he would not retain schools superintendent David Hornbeck. Street skirted the question by saying: "Hornbeck is not the issue."

Katz reiterated his support for vouchers. Street said he opposed them as long as the schools were short of money.

Street reiterated a plan to create a state authority to help oversee school finances similar to the one that was established in 1991 to oversee city finances. The proposal has received a cool reception from Gov. Ridge and the state legislature.

Somehow, some way, the schools must get more money, Street said. He said that as mayor he would let the school system run "pretty much as it has been run." Rather than cut programs, he would let the schools run out of operating money, Street said. Then the state would have to come up with better funding, he said.

"When push comes to shove, we are going to get more resources for the School District of Philadelphia," he said.

Katz replied that such a threat had been tried before, and that the legislature had responded with a school-takeover bill. He said the only result of a state takeover would be that state officials would decide which programs to cut.

"There is a lot of money being wasted in the school system," Katz said. But he also said: "There is absolutely no question that the School District of Philadelphia needs more money."