From the moment Aaron Peskin rejoined the Board of Supervisors eight months ago, he’s been the man of the moment in San Francisco politics.

He’s in the middle of every discussion, disagreement and policy. The kind of public official who uses his weekends to pore over policy papers and contracts, he comes to meetings impeccably prepared and ready to cite chapter and verse.

“He’s making us read EVERYTHING,” groused board President London Breed soon after Peskin joined the board.

But c’mon, he’s the only new addition to the 11-person body. How much influence could he have? A lot, says Supervisor Scott Wiener.

“On a political and policy level, it has changed everything,” Wiener says. “The board is now officially antihousing. And (the progressives) have declared war on the mayor. They have four charter amendments on the ballot to strip power from the mayor.”

Peskin reacts to such criticism with an indulgent chuckle. He points to his work for Proposition C in the June election, which not only created affordable housing but also was endorsed by Mayor Ed Lee.

“This is where I profoundly disagree with Scott,” Peskin said. “I know that’s part of his narrative, but it is just not true.”

The interesting part of the return of Peskin to the board after seven years is that virtually everyone says he is personally charming, and — if the issue is right — easy to collaborate with.

“He’s an interesting man,” says moderate Supervisor Katy Tang. “He can be very charming and funny when he wants to be. On one hand, I appreciate someone who cares as much about the city’s health as I do.”

It’s true. Tang and Peskin may be the board’s odd couple, but they have already teamed up more than once to force a closer look at financial deals and contracts.

Peskin loves to relate when former supervisor and retired judge Quentin Kopp introduced him as “the most fiscally conservative member of the Board of Supervisors.”

“It is kind of weird,” Peskin said. “I’m progressive on social issues, but fiscally conservative.”

However, despite the fact that virtually everyone shares Wiener’s view that Peskin is “one of the smartest politicians I’ve ever met,” he has definitely upset the moderate minority.

Tang’s affordable-housing density bonus plan — which would have allowed two extra stories in buildings that met affordable-housing standards — has faced testy opposition from Peskin and Supervisor Eric Mar that undercut the plan. Tang was miffed that neither Mar nor Peskin checked in with her before proposing their own plan “out of the blue.”

Wiener is still smarting from the progressives’ attempts to undermine efforts to put a sales tax on the ballot to aid transportation and homeless outreach. They also, until a compromise was reached, blocked Wiener’s legislation to require the city to take care of trees on the street.

“They were prepared to kill — not on their merits — well thought-out, broad measures for trees, transportation and homelessness,” Wiener said. “They have definitely been exercising their power.”

And, says progressive Supervisor David Campos, that is the real deal. Forget the cult of Peskin, the simple fact is, with him, the progressives have a 6-5 majority on the board.

“I’ve been on both sides of this,” Campos said. “When you have the sixth vote, it changes everything. I don’t think we’ve been any more partisan than any other majority.”

Maybe not, but the bickering in the board chamber has certainly ramped up since Peskin arrived. The meeting three weeks ago was a low point. Supervisors called each other names, raised voices and mocked each other. Ever the shrewd strategist, Peskin sat back quietly and let the others carry on.

“I was watching them, and I was kind of going, ‘Wow’” Peskin said. “I didn’t say a word.”

OK, if you don’t think Peskin was actively involved in all that, you haven’t been paying attention.

On the other hand, progressive members of the board have sometimes been surprised to find that Peskin isn’t supporting them.

“Having come back to this in midlife, I don’t have this compunction that I should go along with the pack,” said Peskin, 52. “I’m not scared to be the one person who dissents.”

Keep an eye on him. He’s smart, strategic and unpredictable. And even his critics admit if he became mayor — he denies interest — he’d probably do a good job.

I told him he’s providing interesting copy for reporters.

“Anything to help the fourth estate,” he said cheerfully.

C.W. Nevius is a San Francisco Chronicle columnist. His columns appear Tuesday, Thursday and Saturday. Email: cwnevius@sfchronicle.com Twitter: @cwnevius