With five days to go before this nail-biter of an election, Democrat Street took a challenge from Republican Katz. At the morning breakfast hosted by the Greater Philadelphia Chamber of Commerce, Katz said that some of Street's former Council colleagues had not endorsed him.

"The feeling there is that most great ideas that the members have had have been stifled," Katz said. An animated Street broke in, saying: "Do not ever think that somehow you are going to sit here and pretend to be an expert on City Council."

For much of the day, Street's campaign tried to arrange a big Council endorsement for Street, who served as Council president for seven years. Street's campaign said last night that Council Democrats would formally endorse him this morning.

The two candidates also got into it at the breakfast - their fourth joint appearance in 48 hours - over Street's experience in government.

After Street ticked off a list of what city government had accomplished while he was in office, Katz said, "Everything is perfect in Philadelphia if you listen to John Street."

"That's not what I said!" Street cut in.

"Just let me finish this one thing before you interrupt me again," Katz snapped.

Katz did air one new proposal. To lure high-tech companies into the city, he said, he would like to convert the old General Post Office building at 30th and Market Streets - soon to be nearly vacant - into a home for start-up or recently relocated businesses, he said.

The U.S. Postal Service is building a new facility nearer Philadelphia International Airport, which is expected to open in 2002. Katz said the 64-year-old West Philadelphia building has one million square feet of space, and he noted that it is near universities and other resources and just across the street from high-speed train service. He suggested companies could be given three year's free rent in return for a longer-term commitment to stay in the city.

Street and Katz face each other again tonight in the final televised debate of the general election, on WPVI-TV (Channel 6) at 7 p.m.

In the course of their day yesterday, the candidates received conflicting signals from swing voters: liberal Democrats, on whom this election hinges. For Street, State Rep. Babette Josephs, who represents Center City, gave a hearty speech at City Hall saying that Republicans are spending a fortune on the Philadelphia mayor's race because they want to take over the town, the state and the nation. Josephs was among 22 Democratic state representatives who held a rally for Street organized by State Rep. Dwight Evans, who ran in the spring Democratic primary.

At the same time, the board of the liberal Americans for Democratic Action began mailing its 1,200 members letters telling them that for the first time in its 52 years, the group would not endorse a mayoral candidate. It did endorse a few Council Democrats: David Cohen, Angel Ortiz, Blondell Reynolds Brown and Michael Nutter.

This race hinges on swing voters. According to a poll in Wednesday's Daily News, many of the undecided voters are liberal-leaning female Democrats. The poll of 606 likely voters had Street at 39 percent and Katz at 38 percent with the rest undecided.

Mayor Rendell also got into the act yesterday, popping out of his City Hall office in the afternoon to criticize a Katz radio ad that has been running since last Wednesday that says: "Sam Katz says we should try to manage the city 2 percent better. You [Street] attack him for that. Mr. Street, if you don't believe the city can be managed 2 percent better, why are you even running for mayor?"

Rendell called the ad "disingenuous" and said it ignored all the work he and Street did while Street was Council president to cut city spending.

"John Street could cut 2 percent out of the budget blindfolded because he's done it," Rendell said.

He also had kind words for Katz, saying: "Sam Katz will be a solid mayor, and I wouldn't have any reason to fear if Sam becomes mayor. John Street is clearly superior, and he deserves to be elected."

Asked whether it would be painful as head of the Democratic National Committee to have a Republican win next Tuesday's general election, Rendell said, "It would be less painful because I admire Sam Katz and think he's a good guy, and it would be painful if some demagogue had won."

But just to make sure Katz doesn't win, Rendell has gotten President Clinton and U.S. Sen. Edward Kennedy (D., Mass.) to come into town tomorrow for a Street pre-election pep rally.