MOSCOW — For years, the Kremlin tried to disregard the opposition chief Aleksei A. Navalny, proper right down to avoiding the very mention of his name.

However by Sunday, Russian officers had drastically reversed course.

President Vladimir V. Putin’s spokesman appeared on a prime-time present on state tv and denied Mr. Navalny’s assertion that Mr. Putin had a secret palace on the Black Sea. On one other marquee program, the host devoted 40 minutes to Mr. Navalny, who was described as partaking in “political pedophilia.” And the night newscast confirmed tweets by Western officers in assist of Mr. Navalny as proof that he was working towards Russian pursuits.

The tightly scripted, all-hands assault on Mr. Navalny on Sunday underlined how the opposition chief’s dramatic return to Russia per week earlier and his arrest have modified the panorama of Russian politics.

Mr. Putin stays in agency management of the levers of energy. However Russians sad with their president — lengthy a weak, numerous and atomized group — out of the blue have a transparent chief round whom to rally, and the federal government seems not sure about methods to battle again.

On Saturday, tens of 1000’s of Russians took to the streets in assist of Mr. Navalny in additional than 100 Russian cities — protest on a scale unseen within the nation in years. Quiet Siberian cities noticed crowds within the 1000’s, whereas in Moscow, a survey confirmed that greater than one-third of the individuals had by no means protested earlier than.

“Individuals are uninterested in this authoritarian regime, of the chaos, of the corruption,” stated Viktor F. Rau, a liberal activist in a kind of Siberian cities, Barnaul. “Navalny was the spark.”

With extra protests deliberate for subsequent weekend, and a courtroom listening to that might ship Mr. Navalny to jail for years scheduled for Feb. 2, a brand new crackdown on the opposition and a harsh jail sentence for its chief may backfire, sending but extra folks into the streets.

Both method, analysts say, the standoff between the Kremlin and its critics appears poised to accentuate, injecting new volatility into a rustic through which Mr. Putin now has a transparent predominant adversary within the political area.

Mr. Navalny had been a gadfly for years, however his poisoning last summer in what Western officers say was a state assassination try, adopted by his daring return to Russia, sharply raised his stature. The Kremlin denies any involvement within the poisoning.

“For me, that is principally a revolution,” stated Tatiana Stanovaya, a nonresident scholar on the Carnegie Moscow Heart, referring to the brand new breadth of Mr. Navalny’s assist. “We’re going to see an extended interval of confrontation between the opposition and the authorities, and it’s very onerous to say the way it will finish.”

Saturday’s protests introduced collectively the often-feuding parts of Russia’s opposition: pro-Western city liberals, leftists, libertarians and nationalists.

In Vologda, about 300 miles north of Moscow — one of many many far-flung cities that noticed surprisingly giant crowds — the roughly 1,000 protesters rallying for Mr. Navalny included Communists and coronavirus deniers, in keeping with a journalist there. Some folks spray-painted “Putin is a thief” and an obscenity on the partitions of the regional administration.

The journalist, Sergey Gorodishenin, defined the big turnout by folks’s accrued resentments over injustices within the judicial system, native parks being constructed over and the hardships of the pandemic.

“I feel the following protest will see extra folks, not fewer,” Mr. Gorodishenin stated. “We’ve by no means seen something like this in Vologda.”

Mr. Putin has outlasted protest actions earlier than.

In 2012, greater than 100,000 folks demonstrated in Moscow. In 2017, Mr. Navalny spawned one other wave of nationwide unrest. In 2019, the contested run-up to Moscow Metropolis Council elections set off a summer of protest within the capital. And final summer time, 1000’s of individuals rallied weekly within the Far Eastern city of Khabarovsk in assist of a preferred governor who had been arrested after falling out with the Kremlin; greater than six months later, the governor stays behind bars.

Analysts are intently watching how outstanding figures in Russian tradition and enterprise react to the protests. Final week, as an example, social networks have been abuzz that the Russian pop star Alla Pugacheva had unfollowed her pro-Putin ex-husband on Instagram and adopted Mr. Navalny.

Ms. Stanovaya stated that the dimensions of Saturday’s protests had given Mr. Navalny the form of political legitimacy that might lead extra folks within the Russian elite to assist him, at the least privately. A extra violent response to future protests — on Saturday, the police clubbed protesters however avoided intense strategies like tear gasoline — may have additional unintended penalties.

“Individuals are anticipating a rise in violence on the a part of the regime,” Ivan Kurilla, a historian on the European College of St. Petersburg. “The optimistic situation is that such issues provoke some form of crack within the elites.”

Signaling that they might observe a tough line, the Russian authorities introduced a collection of prison circumstances towards protesters, together with for the crime of blocking streets.

Taking part in in Mr. Navalny’s favor is that his blunt, populist, anti-corruption message has struck a chord with a cross-section of society. His investigation printed final week into Mr. Putin’s supposed secret palace — full with particulars like an $850 rest room brush — has been seen greater than 80 million occasions on YouTube, and the Kremlin appeared compelled to take notice.

“Putin is certainly not fixated on rest room brushes,” the state tv host Dmitri Kiselyov intoned Sunday night in a rebuttal of types. “He’s an individual of a totally completely different scale.”

On Saturday, a crew led by Aleksandra Arkhipova, a Moscow social anthropologist, polled a random pattern of 359 protesters within the capital and located that 42 p.c of them had not attended an illustration earlier than this yr. When the crew surveyed the 2019 Moscow protests, that determine was 17 p.c, she stated.

Mr. Navalny, she stated, makes Russians assume twice about issues similar to corruption that they may in any other case merely take without any consideration.

“Navalny says issues that virtually each resident of Russia is aware of to be true within the depths of his soul,” Ms. Arkhipova stated. “He says we must always not settle for this — that this isn’t the pure order of issues.”

One in every of Saturday’s first-time protesters in Moscow was Maria Zhuravlyova, a 29-year-old supervisor at a know-how firm. She had come out along with her good friend Grigory Orlov, 25, to oppose censorship and rights violations underneath Mr. Putin.

“Loads has piled up for folks,” she stated. “I feel we have now an extended street forward of us.”

Ivan Nechepurenko contributed reporting from Moscow. Oleg Matsnev and Sophia Kishkovsky contributed analysis.