“I can see that there are enough people here to seize the Kremlin,” said Mr. Navalny, 35, who listened to the earlier protest on the radio while serving 15 days in jail. “We are a peaceful force and will not do it now. But if these crooks and thieves try to go on cheating us, if they continue telling lies and stealing from us, we will take what belongs to us with our own hands.”

Mr. Navalny especially delighted the crowd with barbed insults of Mr. Putin; indeed, hatred for the prime minister has become a motif at these events. One popular sign read “Putin is our condom,” in a reference to his comments about the white ribbons. Another, painted in the style of Salvador Dalí, showed the prime minister melting in front of a giant clock with the words “Your time has passed.”

“Where is this man?” Mr. Navalny asked. “Can you see him? Is he here?”

He added: “These days, with the help of the zombie-box, they are trying to prove to us that they are big and scary beasts. But we know who they are. Little sneaky jackals! Is that right?” The crowd roared. “Is that true or not?” Another roar.

Pavel Morozov, 23, said he realized that dislodging Mr. Putin might hurt the middle-class quality of life he enjoys. But he said it did not matter. “Putin is a reincarnation of Brezhnev,” he said. He added that while he did not know whether people like Mr. Navalny or the environmental activist Yevgenia Chirikova were worthy alternatives, “at least they are an alternative. Anyone now but Putin.”

Former President Mikhail S. Gorbachev told Ekho Moskvy that he thought Mr. Putin should withdraw his bid for the presidency. When asked whether he thought Mr. Putin would give up power voluntarily, Mr. Gorbachev, who was not at the rally, said, “What’s terrible about it?” and noted that he had done so 20 years ago. “Then all the positive that he has done would be safeguarded.”

For organizers, the challenge is to keep the movement alive at all, since the protesters are working people who will leave the city for two soporific weeks in January. Their commitment to politics is unclear; some say that they are willing to demonstrate for years, others that they will lose interest if a leader does not emerge.