So now Supervisor-elect Aaron Peskin has an official start date. The District 3 leader was voted back into his old job last month, and today we learn that he'll return to work on the 8th of December. Putting to rest speculation that he would delay signing the Board of Supervisors approved, Department of Elections certified election results from November's election, Mayor Lee announced he would sign the results — thus making them official — as soon as he is presented with them. Peskin is not officially a member of the Board until the Mayor does this, and the timing of Peskin's start date will likely have a profound impact on several major projects — including the proposed $380 million new jail.

And, as has been said a lot, Peskin's return to the board also seems to signal a return to some more progressive politics.

In conversation with the San Francisco Chronicle, the mayor made his intention explicit.

“I anticipate him being here on the 8th, and he should be sworn in, and that should be a fact,” said Lee. “I am taking his word he is going to be here.”

This should come as a welcome surprise to Supervisor Avalos, an ally of Peskin, who squawked to the Examiner on Monday that he expected Mayor Lee to delay the start date of Peskin's term by up to ten days — something that Lee has the authority to do.

Peskin's election to the District 3 Supervisor seat that he held for many years in the last decade brings with it a shift in power on the Board of Supervisors from what is considered to be the moderate bloc to the progressive bloc. The proposed new jail, which supporters say is needed to replace the current seismically unsafe jail, is opposed by the more progressive members of the Board who argue that the money should be spent elsewhere.

While Peskin has not officially announced a position on the jail, it is reasonable to assume he will vote to kill the project.

Opposition to the new jail picked up some steam this week, with San Francisco District Attorney George Gascon coming out against the project on Tuesday.

"What San Francisco needs today are mental health facilities, not a new jail,” CBS SF reports the DA as saying at a press conference.

In announcing that he would not delay Peskin's start date, maybe the mayor is signaling that he's already come to terms with the new balance of power, and will be carefully picking his battles.

Peskin, who is currently on vacation in Nepal, is unavailable for comment.

Previously: Mayor Lee Could Delay Start Of Peskin's Term In Order To Push Through New Jail Project