Russia’s do-as-it’s-told parliament showed unusual signs of defiance Tuesday when a minority of lawmakers seized on a mostly unexplored tactic here — the old-fashioned-filibuster — and fought hard and long against a bill that would impose huge fines on protesters.

They had no hope of success — Vladimir Putin’s United Russia party holds 238 of the 450 seats in the State Duma, the parliament’s lower house — but they scored a huge victory nonetheless, making Russians pay attention to a normally rubber-stamp body that rarely makes news. On Tuesday evening the Duma dominated Twitter, running ahead of tweets about two quarreling pop stars and even forcing “Today Is National Hug Your Cat Day” into third place.

In this version of a filibuster, opposition deputies took turns introducing, discussing and voting on nearly 400 amendments to the bill. As midnight approached, nearly 90,000 viewers had watched a Web broadcast of the proceedings, which began just after noon.

“All of a sudden the Duma has become a place for discussion,” declared Gennady Gudkov, a member of the Just Russia party, which led the attack with some help from the Communists.

Just before midnight, the filibuster was cut short, and 241 Duma deputies voted in favor of the legislation. At midnight, the unprecedented session was declared over. The Federation Council, the upper house, promised to pass the bill Wednesday.

“United Russia celebrates its victory,” Gudkov tweeted. “A Pyrrhic victory, which will result in the defeat of Russia. They think they are forever. A stupid mistake.”

Opponents of the bill say it is intended to keep protesters off the streets, stifle freedom of speech and effectively nullify Article 31 of the Constitution, which guarantees freedom of assembly. United Russia was eager to get the measure passed Tuesday so it could be ready to deal with protesters planning a demonstration for next Tuesday.

The bill would raise fines for unsanctioned protests to about $9,000 for individuals, up from $60 now, and as much as $48,000 for organizers, up from $1,160. Those unable to pay would be ordered to perform up to 200 hours of community service. Such punishments represent an outsize penalty in a country where the average yearly salary is about $20,700.

Gudkov and other deputies introduced amendments to the legislation changing a comma here, a fine there; adjusting 200 hours of community service to 20; and exempting war veterans and minors. Every one went down to instant defeat on an electronic voting system. Few deputies were in the hall, but the United Russia leadership said those who were present had the power to vote on behalf of their absent colleagues.

In an article published Tuesday, Sergei Neverov, a United Russia official, wrote that the public needs more protection against reckless protesters — though most demonstrations have been peaceful.

“The freedom of one must not pose threats to others in conditions of real democracy,” he wrote. “That is why really democratic countries live according to the principle: The law is harsh but it is the law.”

The protest movement began in December, in anger over the Duma elections and in pursuit of a more democratic country. Many voters described the elections as rigged. United Russia, by official count, took about half of the vote, even though the party’s popularity was perceived to be falling.

Human Rights Watch said the high fines would have a chilling effect on peaceful assembly. “The aim seems to be to curtail demonstrations rather than to properly regulate them,” said Hugh Williamson, the organization’s director for Europe and central Asia.

On Tuesday afternoon, about 20 demonstrators protesting the bill were arrested outside the State Duma.

On Tuesday night, Gudkov accused United Russia of using its majority to ride roughshod over Duma rules.

“There are very few members in the hall,” he tweeted, asserting that the Duma was voting without a quorum. “Simply outrageous!”