“I am an opponent of populist rhetoric, the existing economic course suits me, and I am happy to explain to anyone that for the average entrepreneur, United Russia is better than the Communist Party,” he wrote. “I am also an opponent of revolution: I have an elderly mother and a young daughter. But, please, can you in return show a little respect to me, to my workers, and to common sense?”

Until now, they have occupied a neutral position in Russian politics, this group. Of 80 employees, only one admitted to voting for United Russia, Mr. Pitirimov said. And only one routinely participated in anti-Kremlin demonstrations, hesitating to invite his co-workers since, as he put it, “these events often end with detentions and clubs.”

In December, this changed with amazing speed. The night after Mr. Kazakov was detained, Ms. Lukyanovich left work and stood on the edge of a crowd that had gathered for the second time to protest violations in the parliamentary campaign. She was just watching, like a swimmer dipping her toe in the water. It was the closest she had been to a protest in her 23 years, she said.

“It is difficult to say what in particular brought me to the idea that it was worth taking part,” she said. “I looked at it and realized it was not as scary as I thought, and probably it was then that I decided I would attend the next rally.”

That opportunity arose four days later, when a crowd of about 50,000 people was organized via a Facebook page. Mr. Terekhov expected five or six of his employees to attend, and was shocked to discover the number was far higher, more like 20 or 25. Ms. Fotchenko, his account manager, went because “the truth is, it was interesting to see what was happening.”

When she got there, she said, “my consciousness was turned upside down.” Her emotions were so powerful, she said, that she was afraid to share them on Twitter lest she come off as “histrionic.”

“I am 35, and this has happened to me for the first time,” she said. “I thought, probably not everything has been lost.”