Just 11 days before Philadelphians pick the first mayor of the 21st century, the horse race between Democrat John Street and Republican Sam Katz is still neck-and-neck.

A new independent poll by the Greater Philadelphia Chamber of Commerce of 450 randomly selected likely voters found Katz and Street deadlocked at 43 percent, with 14 percent still undecided in the race's waning days.

Meanwhile, Katz tried to make a move yesterday by launching his first radio ad that's critical of Street on the issues. The new spot complains that the Democrat has said he'd change little about Philadelphia's troubled schools, while Katz supports major reforms.

"What is Mr. Street thinking?" asks the ad, which was heard on KYW-AM and WPHT-AM. The new commericial comes in the wake of reports in the Daily News that some school employees haven't been paid for weeks while some dead workers got checks, although the commercial doesn't mention that specifically.

The ad ran on the same morning that the Inquirer quoted Katz as saying, "I don't have to" go negative on Street. The paper reported Katz expected to win and saw no point in turning around to trip the man behind him.

"It's just an ad - I don't characterize our ads," Katz's campaign manager Bob Barnett said when asked if the new spot was a negative ad. In keeping with the Katz campaign's policy, Barnett said he couldn't release a transcript.

For much of the campaign, Street has been the one seeking to place Katz on the defensive on education issues, saying that the Republican's support of vouchers - government checks to parents of parochial and private school students - is a radical plan that would weaken public schools.

Katz has said that vouchers would help pry more funds for public schools from the GOP-led government in Harrisburg and that anything that might make schools better should be tried.

The Street campaign recently started posting streaming versions of its TV ads, including those that have attacked Katz's positions on school vouchers and taxes, on its Web site, www.street99.com.

"Obviously Sam Katz has not made a gut level connection with people, and he's sagging and needs to be negative," said Ken Snyder, Street's campaign spokesman. "How can you trust a candidate who says that he's not going to run negative ads on the same day he starts running negative ads."

Meanwhile, the Chamber of Commerce poll released yesterday showed what two earlier independent surveys also indicated - that in spite of all of the ads, debates, forums and news articles in recent weeks, neither candidate seems able to break free from the other.

The chamber's earlier poll, conducted last month, had Street leading by 42-39 percent, but that was within the 3.9 percent margin of error.

"It means that the race is more competitive than we've seen in a number of years and that's good, that means that people's vote makes a difference," said Joe Mahoney, the chamber's senior vice president.

In another matter, members of the Philadelphia Interfath Action, a coalition of 40 churches, synagogues and associations, stood outside City Hall yesterday, announcing that they have the signatures of more than 2,000 city residents in support of its agenda calling for better wages for city residents, safer neighborhoods and redevelopment of the Logan sinking home area.

The Rev. Isaac Miller, pastor of the Church of the Advocate, said PIA is aiming to get 10,000 signatures and then - prior to the Nov. 2 election - release scorecards that show how Katz and Street stack up against the group's agenda. So far, Miller said Katz has supported more PIA issues than Street.

"We also have to say that Mr. Katz has been more accessible to us but that doesn't mean John Street won't have an opportunity to meet with us," he said.

Staff writer Mark McDonald contributed to this report.