At a news conference at a fire station in the Northeast, U.S. Rep. Robert A. Borski and City Controller Jonathan A. Saidel said Katz's proposal to cut the wage tax to 4 percent - a deeper cut than Street has proposed - would leave the city so short of revenue that police and fire protection and other basic services would suffer.

Soon afterward at City Hall, Rendell stepped before reporters to deliver the same message.

Katz's plan "would jeopardize the fiscal stability of the city," Rendell said.

"It should be frightening to people," Street said at the firehouse at Cottman and Loretto Avenues.

Katz's campaign manager, Bob Barnett, said Street and his allies were acting irresponsibly by trying to stir up fear over Katz's tax proposal before the candidate had released a detailed plan on it. Barnett said the plan would be issued soon.

With barely a month to go in the most competitive general election for mayor in at least a decade, Street, the presumed front-runner a few months ago, is campaigning like an underdog.

Even Rendell, Street's partner in city government for seven years and one of his most energetic boosters, said he thought the race was "50-50."

Street will introduce new TV ads tomorrow criticizing Katz, and he plans to hold daily news conferences to hammer away at Katz on his proposed tax cut, demanding that he specify how he would cover revenue losses.

Street's real desire is not to get a meticulously detailed plan out of his rival, but to make him appear fiscally reckless.

The motive for Street's change of strategy is simple: He needs to energize his base - the city's 734,000 registered Democrats, who outnumber Republicans nearly 4-1.

Responding to yesterday's attacks, the Katz campaign said it would release details of the tax plan on its timetable, not Street's.

"There are a lot of things to talk about during the campaign, and we'll talk about them," Barnett said. "We'll give all the information people need to vote. We will be talking about what his proposal is in reducing city taxes and how he's going to do it."

In February and again during a televised debate over the weekend, Katz said he would cut the wage tax for city residents, now 4.61 percent, to 4 percent by 2004, the end of the next mayor's first term.

The wage tax is the city's main source of cash, bringing in more than $900 million a year - 53 percent of all city tax revenue.

Street, as City Council president, worked with Rendell to trim the wage tax in small amounts each year beginning in 1995. Those cuts have brought the rate for city residents down to its current level from nearly 5 percent.

Street favors continuing with the gradual cuts outlined in the city's current five-year fiscal plan, which calls for reducing the tax to 4.46 percent by 2004.

At the news conference outside the Northeast fire station, Street said that firehouses across the city might be forced to close if Katz fulfilled his pledge for a deeper cut.

Street sought to depict Katz as financially irresponsible - willing to sacrifice the needs of Philadelphia residents for the sake of tax cuts.

Street said the Katz proposal would cost the city $500 million in tax revenue.

Rendell administration officials say each cut of 1 percentage point in the wage tax costs the city $200 million a year in revenue. The difference between Katz's proposed cut and the reduction envisioned in the five-year plan is 0.46 percentage points - about $92 million a year in revenue, officials said.

Street had a snappy slogan to go along with his Katz attack: "Where's the plan, Sam?"

That was the headline on a Street news release. The candidate echoed it again and again yesterday.

His surrogates took it up a notch.

Rendell said Katz "doesn't have a plan to do it, and the reason is there is no way to do this other than depending on fanciful things that are almost certain not to happen, and it's going to hurt city services dramatically."

Rendell said that if Katz cut the wage tax to 4 percent, the city would have to cut basic services such as police and fire protection, libraries, the Fairmount Park system, and trash collection. That would be "debilitating," he said.

Responding for Katz, Barnett chided Rendell for criticizing Katz's plan before its release.

"How can he [Rendell] say that it would jeopardize any of those things until he reads the plan? The responsible thing for Ed Rendell to do is to continue to act as a mayor, not as the head of the Democratic National Committee," Barnett said. "Sam Katz is not going to avoid taking positions in the campaign because Ed Rendell might not like it."

There was a bit of irony in Saidel's joining Street to complain that the Katz plan could wreak havoc in the city.

Barnett pointed out that Saidel, during the primary campaign last spring, defended Democratic mayoral candidate Marty Weinberg when he offered a tax-cutting plan similar to Katz's.

"I did endorse that plan," Saidel said yesterday, "but if you look carefully at the plan of Marty Weinberg, you will find that there are a lot of 'ifs' and 'buts.' "

Barnett also noted that in 1994, Saidel proposed a deep wage tax of his own. He wanted to cut it to 2.96 percent over 10 years.

Saidel said: "The reality is that what I thought in 1995 might not necessarily be what I think in 1999."

Borski, the senior member of the city's U.S. House delegation, sought to link Katz to the Republican leadership in Washington.

House leaders, he said, recently proposed to slow income-support payments to the working poor. At the same time, he said, House leaders want to give tax cuts to "the wealthiest Americans."

"The Republicans have only one idea," Borski said - to cut taxes.

For more than a week on the campaign trail, Street and supporters have been trying to stop Katz from making inroads into Street's Democratic base by arguing that if Katz is elected, it could help Republicans capture other major offices.

This is the second wave of Street attacks on Katz. Ten days ago, he launched a TV ad depicting Katz as a radical on education issues who wanted to drain money from public schools by issuing vouchers to pay for private school tuitions.