An undaunted Street plugged right ahead with his attempt to paint Katz as a radical bent on ruining the public schools and dismantling city services for the sake of tax cuts.

With four weeks remaining before the Nov. 2 election, Street, a Democrat, vowed to be unrelenting in his new role as the aggressor in a campaign that Mayor Rendell, a Street supporter, has called a "50-50" toss-up.

"If [Katz] accuses me of negative campaigning . . . he should see what's going to happen next week," Street said at a news conference yesterday.

Street advisers said later that their candidate may have been referring to a TV ad his campaign will begin airing next week. They would not divulge its contents.

Katz, the Republican nominee, introduced a 60-second radio ad yesterday that tells listeners: "Street has been running negative commercials distorting Sam Katz's position on education."

"So before Mr. Street goes any further," a narrator says, "here are the facts: What Sam Katz has said is, we need to try everything to make Philadelphia schools better - smaller class size, better discipline, more help for teachers, more money, and giving parents choices. Anything we can do to stop people from leaving Philadelphia because of the schools, we should."

The ad ends: "We need more from the next mayor of Philadelphia than the negative campaign of John Street."

Since Sept. 26, Street has been airing a 30-second TV ad that contends that Katz wants to privatize the city schools.

It includes a photo image of a 1994 article from the Pittsburgh Post-Gazette with a headline that says: "Cut Taxes by 30% and Watch Schools Improve, Candidate Says." The article refers to Katz, who at the time was a candidate for governor.

The Street ad suggests that Katz's proposal for a 30 percent cut in property taxes statewide showed him to be irresponsible. Katz has mentioned no such idea in the current campaign.

In a series of news conferences over the last five days, Street has attempted to portray Katz as irresponsible in his aim to lower the wage tax paid by city residents from the current 4.61 percent to 4 percent or lower by 2004, the end of the next mayor's first term.

Street, who favors the more modest tax cuts outlined in the city's five-year financial plan, went to a fire station in the Northeast on Monday and suggested that city services, including police and fire protection, would have to be cut to make up the $500 million that Street said would be lost over four years if the tax were reduced to 4 percent.

Yesterday, he made the same pitch in a news conference at Congreso de Latinos Unidos, a social-service center in Girard Avenue on North Philadelphia that receives city funding.

Again, he demanded that Katz produce a plan to show how he would make up the lost revenue. Yesterday, Street had refined his estimate of the loss to "$360 million on the low side to $550 million on the high side."

If services had to be cut, Street said, the community center, which includes services for women and children, might be a "target."

"Once again," said Street, "I call upon my opponent, Sam Katz: Tell us your plan. Where is the plan?"

In an interview later, Bob Barnett, Katz's campaign director, gave the same reply that the Katz camp had been giving for days: It's coming.

"The Katz campaign will release its plan for reducing taxes in a timely way for everyone in Philadelphia to make a decision as to who's got the best proposal," Barnett said.

Barnett would not say why Katz was continuing to give Street an opening to fault him for the lack of a plan. Nor would he say why it took Katz nine days to respond to the Street ad. He said he would not discuss campaign strategy.

Katz says he does not believe that Street's recent assault has hurt him politically. That may be one reason for the Katz strategy. Polls in both mayoral camps show the race to be close. Weeks ago, Street had a big lead in surveys conducted by his pollsters and a small lead in those conducted by Katz's consultants.

David Axelrod, who makes Street's commercials, said yesterday it was ironic for Katz to accuse anyone of negative campaigning. He noted that Katz, though a Republican, had injected himself into the May Democratic primary with radio and TV ads that sharply attacked two of Street's opponents.

"At least our ads are based on issues," Axelrod said.

One target of the Katz ads in May was Marty Weinberg, who has since endorsed Street for mayor.

Street's criticism of Katz's proposal to reduce the wage tax to 4 percent is an echo of the criticism he leveled at Weinberg for a similar proposal.

Weinberg, in an interview yesterday, said the difference between his plan and Katz's is that he said how he was going to cover the revenue losses and balance the budget. He said he would find $55 million in pension savings, get $65 million in new state funding, save $48 million in city employee benefit costs, save $27 million by eliminating 163 jobs, and trim $45 million from the budget of the city Department of Human Services.

Weinberg said that Katz, who has cast himself as an issues candidate, has out put "very few position papers."

"I don't think Sam has put out any specifics," Weinberg said yesterday. "There are only four weeks to go, and there have been no specifics at all."