SAN FRANCISCO — As San Francisco’s Board of Supervisors prepared to vote Tuesday on an ordinance forbidding city agencies to use facial recognition technology, some proponents of the measure were uncertain if they had the necessary support. Two of the legislators who were for it had called in sick.

But Brian Hofer, a paralegal who had drafted the ordinance, seemed unfazed. Sitting in the back of a chamber in City Hall, he wrote and rewrote a draft of a post for Twitter in which he would proclaim victory after the ban passed.

Mr. Hofer, 41, had reason to feel confident. Over the past five years, he has drafted 26 privacy laws for cities and counties in California. All were approved, 23 unanimously. And he had seen enough of the machinations of decision-making to be certain that this one would go through.

“He’s just omnipresent and very effective,” said Lee Hepner, a legislative aide to Aaron Peskin, the city supervisor who sponsored the facial recognition ban. “He’s great at bringing down the volume and making it a level-headed conversation.”