Even on a day when he kept a relatively low profile, businessman Tom Knox continued to dominate the dialogue in Philadelphia's Democratic mayoral primary.

At City Hall, six council members held a news conference to blast his Wednesday endorsement of City Councilwoman Jannie Blackwell as the next council president, calling it inappropriate meddling in Council's affairs.

Outside the building, a coalition of political activists announced that four mayoral candidates had signed a petition calling for public financing of city elections - a move spurred in part by Knox's self-financed campaign.

And in East Falls, candidate Dwight Evans traveled to the public housing project where Knox grew up, Abbottsford Homes, to collect the endorsement of the tenant representatives in the city's public housing developments.

The six council members criticizing Knox were Frank DiCicco, Bill Greenlee, Jim Kenney, Joan Krajewski, Donna Reed Miller and Marian Tasco - all of whom are supporting other mayoral candidates.

"He [Knox] has no right to try to dictate to this council before he even gets elected," said Krajewski. "I'm very angry about it."

Added Kenney: "I really do believe, and I think we all concur, that this is not a good sign for what a Knox administration would be like."

Blackwell, who tried and failed to unseat Council President Anna Verna in late 2003, seemed surprised by her colleagues' reaction to the deal she struck with Knox. But she did not lash back.

"They have a right to criticize. I accept that," she said.

Knox, in a live interview on NBC10, defended his backing of Blackwell for Council president, saying a mayor needed a close ally leading Council to get things done.

Asked whether he was undercutting his image as an outsider by selecting her, he replied: "You have to pick someone in City Council, and everyone there is an insider."

As for the petition calling for public financing of elections, backing came from Democrats Evans, Chaka Fattah and Michael Nutter as well as Republican Al Taubenberger.

The petition was circulated by MoveOn.Org, Common Cause/Pennsylvania, Philadelphia Forward and the Public Campaign Action Fund. There could be no public financing without action in Harrisburg.

At Abbottsford Homes, Evans received the endorsement of the Resident Leadership of Public and Assisted Housing, whose members represent more than 80,000 residents of public housing.

The fact that Knox lived at Abbottsford as a child had little impact on some of the representatives. "Since he loves Abbottsford so much, how much has he given back to Abbottsford?" asked Corliss Gray of Queen's Lane.

But Patricia Thomas, who works in a health center at Abbottsford, said she was still torn. "It's going to be tight. You have a lot of good candidates - Knox, Evans, Fattah. It's between Knox and Evans for me."

In other developments, Fattah received the endorsement of the Valiants, an organization representing 500 African American firefighters.

At a ceremony in West Oak Lane, the group's president, Derrick Sawyer, praised Fattah, saying the congressman "adheres to the same principles that we do."

Nutter - who is being endorsed by the Philadelphia Daily News this morning - picked up two other endorsements at an afternoon news conference at the Water Works Restaurant.

One came from Clean Water Action, a nonprofit environmental group that claims more than 10,000 members. Alisha Deen-Steindler, the group's spokeswoman, said that Nutter "gets it" on issues of environmental sustainability.

Also backing Nutter was Philly for Change, a progressive political organization that says it has 2,000 members. Group vice chair Hannah Miller said that members "will be at the polls in a big way on May 15."

Bob Brady spent the day in Washington, chairing a hearing in his new role as interim chairman of the Committee on House Administration.

Yesterday morning, Evans, Fattah, Nutter and Taubenberger participated in a forum on business and health issues attended by about 150 of the city's business leaders.

The subject of how to lure business into Philadelphia, given the city's high taxes, was among the prime topics.

Fattah laid out his plan to bring in outside businesses, a plan that calls for letting a newly arrived company pay the city's business taxes or the taxes in its current locations whichever is less, for the first five years.

Nutter challenged the fairness of the concept, saying it would put existing local businesses at a competitive disadvantage.

Fattah replied that the idea of giving out selective tax breaks to help the city's economy is already in place - both in the tax abatements for new residential construction and in the various geographic zones where businesses get tax exemptions.

"This is the same concept all of us are applauding under other circumstances," he said.

To read our profiles of the candidates, along with their campaign promises, our reporters' blog and more, go to http://go.philly.com/mayor.