It took the best part of an hour, but a debate eventually broke out among the six Democratic mayoral candidates Monday night.

The first inkling they might harbor conflicting views came with former City Councilman James F. Kenney's mention of Selma, Ala., and a need to be sure Philadelphia's police know the history of the civil rights movement.

That was enough raise State Sen. Anthony Hardy Williams' pulse and voice.

"That is insulting to a generation who know the significance of Selma," said Williams, who then derided one of Kenney's signature legislative achievements, the reduction of penalties for possession of marijuana.

"This is not about some kid smoking weed who has to go to work on Monday, who has to pee in a cup and then get fired. This is about the truth. The truth is, we need to take action, not talk about it."

Kenney never took an opportunity to return the favor, but the display showed a contrast and contention that until that moment had been missing at the candidates' third formal debate, held at the Temple University Performing Arts Center.

The first hour consisted mostly of a well-rehearsed rehash of the positions that, for the most part, all the candidates share.

The most contrary candidate initially was T. Milton Street Sr., who was dismissive of his opponents' promises to help the poor.

"All that sounds real good," the former state senator said, "but until these poor people vote, they are going to be ignored."

Williams' shot at Kenney signaled a shift in tone that continued when the candidates were permitted to question one another.

Kenney - the perceived front-runner - found himself the target.

Nelson A. Diaz, a former judge, took the first shot, asking Kenney why he had stood still for a group photo with City Council candidate Manny Morales, who has become something of a pariah as result of racist and homophobic Facebook postings found on his account.

Morales had "photo-bombed" him, Kenney said.

Next, Lynne M. Abraham went after Kenney for his support from so-called independent expenditure groups, which have no legal contribution limits. The former district attorney used the term dark money to describe the groups.

Kenney said there was nothing dark about the funding, as the groups would be required to file campaign finance reports, just like the candidates.

He swung back, saying Abraham was the only candidate not to release three years of back tax returns. Abraham has released only one.

"Is there a dark money problem?" Kenney asked.

Abraham said she had nothing to hide and would release returns for the other years.

Given a chance to question another candidate, Williams chose Kenney as well, homing in on Kenney's outside activities when he served on City Council.

He noted that Kenney, as a councilman, served on the board of directors of Independence Blue Cross and as an employee of the architectural firm Vitetta. He seemed to imply that those positions - both lawful and oft-reported over the years - posed conflicts of interest for Kenney.

Kenney said that he had received the city solicitor's approval for his position on the IBC board, and that any city work handled by Vitetta had been secured before the firm hired him.

Kenney said he would give up both positions if elected mayor.

In response to an earlier question from moderator Dave Davies, Kenney said he would not appoint controversial labor leader John "Johnny Doc" Dougherty to any key boards or commissions if elected. Dougherty is the head of the electrical workers union and a key financial backer of Kenney's.

Doug Oliver, too, had a question for Kenney, who earlier in the campaign had said he would vote for Oliver, a former PGW vice president, if he could not vote for himself.

Why? Oliver asked.

Kenney got as far as, "Well, you are very articulate. You are young, and I think you're handsome" before he was interrupted by the audience's laughter.

So there would be no misunderstanding, Kenney continued: "I'm not trying to date you."

The debate, part of the Next Mayor project, was sponsored by The Inquirer, the Philadelphia Daily News, and, with partners WHYY, Temple University's Center for Public Interest Journalism, the Committee of Seventy, WURD Radio, Young Involved Philadelphia, and Technically Philly. Along with Davies, the event was moderated by Daily News editorial page editor Sandra Shea.