Most who follow city politics though Lee would run, and for the most part, the reaction has been predictable. Lee joins a crowded field of candidates, 36 altogether. Most political observers believe nine of them are serious contenders, and Lee makes it 10. Those same observers believe he is instantly in the lead.
The fireworks started the moment Lee filed for mayor Monday. Not only literally, as he attended the opening of a youth center in the Bayview, but also politically as he was signing his papers at the elections office.
"Mr. Lee are you going to step down because you lied to the Board of Supervisors?" shouted a heckler who began harassing Lee about going back on his word. Police had to remove the man.
And at the ribbon-cutting, he got a taste of what campaigning may be like.
"The mayor is refusing to help us," said an onlooker. "He's only helping being culturally biased."
Lee said in the seven months he's been mayor, it hasn't been politics as usual. He had changed the culture.
"As we changed the tone of government, started making some very positive headway into all the things that we'd been doing, I changed my mind as result of that," said Lee.
The once reluctant politician said he changed his mind because so much had been accomplished and that there was much more to do. Some of his new opponents quickly went on the offensive.
"One regret that I have is that we all took him at his word and obviously that has changed," said San Francisco Board of Supervisors President David Chui.
"After talking to powerful people he has decided that he's going to throw his hat into the ring, so I think San Francisco voters have a legitimate question about whether he's his own man," said San Francisco City Attorney Dennis Herrera.
Lee pointed to his successes with getting a budget passed on time, pension reform and creating local jobs. He admits it was because of his ability to work well with the supervisors. But the honeymoon may be over.
"I think those successes were predicated on fundamental trust, and I think with that trust having changed, that is most likely going to change the dynamic at City Hall," said Chiu.
Lee's handlers tell ABC7 that he called most of the supervisors Sunday night to explain his position. Two of them, Chiu and John Avalos, are also running for mayor. Chiu is disappointed with Lee because as board president he championed much of Lee's agenda with the Board of Supervisors.