By Mike Dunn

PHILADELPHIA, Pa. (CBS) — There was a major development today in the 2015 Philadelphia mayor’s race: after weeks of indecision, City Council president Darrell Clarke says he will not leave his Council post to run for mayor.

READ MORE: Pennsylvania US Senate Race Between Republicans Mehmet Oz, Dave McCormick Too Close To Call

Clarke, in an interview with KYW Newsradio, said a “significant number” of people urged him to run for mayor.

“I listened to all of those conversations and did an anlysis as to whether or not that was something I wanted to do,” he said, “but at the end of the day I really enjoy being Council president of the City of Philadelphia, and I really enjoy being the councilman of the 5th District.”

By law, Clarke would have had to resign his Council seat to run for mayor. He had been courted by many of the city’s labor unions to jump into the mayor’s race, but he was clearly conflicted about the idea and spent the last few weeks privately seeking advice on the question.

Today, he explained why his decision was so long in coming:

“It’s quite flattering when people come to you, in the business community, the civic community, the labor movement, all across the board. You have to listen to that, and you have to give some thought to their concerns about who would play as the mayor of the City of Philadelphia.”

Clarke would not say if he will endorse any of the other mayoral candidates.

Clarke is completing his fourth term on City Council and first term as Council president.  And as president, Clarke achieved what few of his predecessors were able to:  gaining the support of all 16 other councilmembers, to the point where Mayor Nutter was unable to get some key legislation — such as his plan to sell PGW — introduced and debated.

The Democratic primary this coming May is the key to the mayoral race in this heavily Democratic city.  So far four people have announced: former Philadelphia DA Lynne Abraham, former city solicitor Ken Trujillo, state senator Anthony Williams, and onetime state representative Milton Street.

READ MORE: John Fetterman Wins Democratic Pennsylvania Primary For Senate, AP Projects

Doug Oliver, a former spokesman for Mayor Nutter, recently resigned his job as a vice president at PGW in expectation of running for mayor.  Another likely candidate is another former city solicitor, Nelson Diaz.

So, the field is crowded.  But if Clarke had entered, he would have immediately been considered one of the frontrunners by virtue of his current post and union support.

It was the potential of a Clarke mayoral bid — and the ensuing union support — that led city controller Alan Butkovitz to rule out a run for mayor.

Hearing about Clarke’s plans today, Butkovitz said “it leaves a tremendous vacuum in the mayoral race,” noting that Clarke had substantial support among political, business, and labor leaders.

(Philadelphia controller Alan Butkovitz.  File photo by Mike DeNardo)

(Philadelphia controller Alan Butkovitz. File photo by Mike DeNardo)

—–

Now, Butkovitz says, he will revisit the Philadelphia political community, think about changing his mind and rejoining the race at this point.

He says he will take the pulse of people who are “capable of raising money” and then determine whether he should rejoin the fray. Butkovitz thinks a successful candidate will have to raise about $3 million.

MORE NEWS: Phillies Return Home After Road Trip With 3-0 Loss To Padres