Three-time Philadelphia mayoral candidate Sam Katz won't give it a fourth go this fall.

Katz announced his decision via e-mail Tuesday afternoon, thanking supporters for encouraging him to run.

His e-mail thanked "everyone . . . who thought that Philadelphia was ready for an independent candidacy - for my candidacy - and who said they would be there to help me if I chose to go again."

Thus ended months of speculation. In February, Katz switched his registration from Republican to independent - a sure sign, many thought, that he would jump into the race after Tuesday's primary.

As recently as last week, he said, he was a candidate in every way except publicly announcing it.

"I was running last week," he said. "I had signed up a campaign manager. I had started to put together the pieces for fund-raising. I had started reaching out to political people."

A three-hour walk Sunday along the Cresheim and Wissahickon Creeks was when that all changed. Katz said he made some phone calls along the trail and did some thinking. "I did what people who are making big decisions do," he said.

He came out of the woods no longer a candidate.

One of the first people to learn of his decision was former City Councilman Bill Green, who is now on the School Reform Commission and is another oft-mentioned possible independent mayoral candidate.

Katz said he and Green have a "growing working relationship" and mutual respect. He saw Green as "someone who would have been a really important player" in his campaign if he had run.

And Katz is more than willing to play that role if Green runs.

"He and I have had a number of conversations over the last couple of weeks," Katz said. "If Bill decides that he wants to do this, I'm going to support him."

Katz, 65, had a career in public finance before he ran for mayor as a Republican in 1991, and then in 1999 and 2003, losing the last two races to John F. Street.

"In the past," his e-mail said, "I felt a powerful desire to serve in this role. But to pursue the mayoralty of Philadelphia demands a burning passion for the job. I had that passion in the past. I recognize the difference today."

He now runs History Making Productions, a local filmmaking company that will document much of Pope Francis' visit in September.

Katz said he was not prepared to endorse any of the current mayoral candidates - six Democrats and Republican Melissa Murray Bailey. He said he hopes another independent joins the fall race and called the candidate conversations leading up to the primary lacking in substance.

"Big issues are usually debated, big problems are discussed - that didn't happen and it certainly won't happen in the general election unless there's an independent candidate. As nice as Melissa Bailey is, she only raised $4,000. I don't think she'll be heard," Katz said.

Green, for his part, said the news that Katz would not run was "a loss to the conversation."

As for his own plans for November, Green - whose father was mayor in the early 1980s - said only: "I've kept my options open and I'm not prepared to close them down." 215-854-5506 @juliaterruso