While nothing like some of the attack ads seen in the primary, the new commercial signals a more combative tone in the race, which has just five weeks to go.

In the 30-second spot, an announcer says that Katz wants to "privatize" public schools with school vouchers, and that Katz has talked about cutting school taxes. It then notes that as City Council president, Street passed a liquor tax to fund schools and held a citywide summit to study ways to fix the public schools.

The advertisement tries to define Katz as a Republican not only by calling him one but by stressing his position on vouchers, which is shared by Republicans around the state.

And it emphasizes that Street is a Democrat. In a city with 187,000 registered Republicans and 734,000 registered Democrats, Street is reaching into his base to keep wavering Democrats in line behind him. Katz, however, has been picking away at those swing voters, hoping to build a winning coalition.

The problem with the ad, according to Katz's campaign director Bob Barnett, is that Katz's position is distorted and dated.

"Their intent is to confuse and distort and be negative," Barnett said. The ad shows a headline from a 1994 Pittsburgh Post-Gazette saying "Cut Taxes by 30% and Watch School Improve, Candidate Says." The story was written in 1994, when Katz was running for the Republican nomination for governor.

Barnett also said that the ad shows Street is running scared because he is attacking Katz.

"They're just throwing mud against the wall to see what will stick," Barnett said.

Katz does favor school vouchers, but he argued before a group of Center City residents earlier this week that they could be used as a wedge to pry more money from Harrisburg to fund Philadelphia's public schools.

He noted that the city's popular Democratic mayor, Ed Rendell, has been unable to draw more state money for city schools and that the state's equally popular Republican governor, Tom Ridge, has been unsuccessful in getting a voucher bill through the state legislature.

There is room for some kind of compromise, Katz said.

Street has campaigned against vouchers, saying they would take too much money away from the public schools, further jeopardizing their more than 200,000 students. Street's wedge would be to trade off some kind of state oversight on school finances for more state funding.

Street spokesman Ken Snyder said the candidates' positions offer a "natural contrast" between them. Noting that Katz has yet to issue a position paper on the public schools, he added, "He's advertising that he has plans, but he won't tell you what they are."