Aleksei A. Navalny built Russia’s largest opposition force in his image, embodying a freer, fairer Russia for millions. His exiled team now faces the daunting task of steering his political movement without him.

The movement has found a leader in Mr. Navalny’s widow, Yulia Navalnaya, who has presented herself as the new face of the opposition to President Vladimir V. Putin. Ms. Navalnaya, 47, is aided by a close-knit team of her husband’s lieutenants, who took over running Mr. Navalny’s political network after his imprisonment in 2021.

Maintaining political momentum will be a challenge. Few dissident movements in modern history have managed to stay relevant, let alone take power, after the death of a leader who personified it. And so far, Mr. Navalny’s team has made little attempt to unite Russia’s fractured opposition groups and win new allies by adjusting its insular, tightly controlled ways.

A spokeswoman for Mr. Navalny’s team, Kira Yarmysh, did not respond to questions or interview requests; nor did several of Mr. Navalny’s aides.

In their public statements, Mr. Navalny’s top aides have said their movement will have to change to continue confronting Mr. Putin without its leader, though it is unclear what the new strategy might be.

Even from prison, Mr. Navalny had “managed to support us, to infect us with optimism, to come up with projects, come up with cool political ideas,” Leonid Volkov, Mr. Navalny’s chief political organizer, said in a video published on social media last month. “Without Aleksei, things will not be as before.”

But, Mr. Volkov added, he did “not have a concrete plan of action.”

Images of thousands of Russians who paid respect to Mr. Navalny at the cemetery last week despite the threat of repression have provided Ms. Navalnaya with political momentum. Her ability to channel this impulse into a lasting political force will be tested during Russia’s presidential elections this month.

Mr. Putin is all but certain to win his fourth six-year term in a vote that lacks real competitors. But to disrupt the government’s narrative of widespread support, Ms. Navalnaya has taken up an initiative first supported by her husband. It calls on voters to head to voting stations at 12 p.m. on March 17, the last day of the three-day vote.

What voters choose to do once they are at the polls is less important, the initiative’s supporters say, than registering protest against a sham election with their mere presence.

“We can show that we are many, and that we are strong,” Ms. Navalnaya said in a video published on Wednesday.

By framing the initiative, called Midday Against Putin, as a tribute to Mr. Navalny, Ms. Navalnaya has presented herself as his political successor.

But staking the political capital of Mr. Navalny’s movement on a risky, hard-to-measure expression of civil disobedience could also expose the limits of Ms. Navalnaya’s reach.

“If no one comes out, it will change my perception of the country,” said one of the initiative’s authors, Maxim Reznik, a former regional lawmaker from St. Petersburg living in exile. “Are people afraid to such an extent that this is now all so hopeless?”

After long shunning the public spotlight, Ms. Navalnaya has begun building her political persona in sharply produced, focused monologues presented in short YouTube videos, as well as through poignant public speeches to Western policymakers.

But she has avoided giving interviews to news media or going off-script in other public events.

She is supported by a team made up of Mr. Volkov and about four other people who were senior aides to Mr. Navalny. Most are in their 30s and spent years working with Mr. Navalny as he challenged the government.

After the government labeled Mr. Navalny’s movement extremist in 2021, his team moved operations to Vilnius, Lithuania, because of its proximity to Russia and physical safety. At least seven people who remained behind and had worked for Mr. Navalny as activists or lawyers have since been imprisoned in Russia.

In Vilnius, Mr. Navalny’s team has equipped a warren of offices, conference rooms and broadcast studios in a central office building as the headquarters of its political organization, the Anti-Corruption Foundation.

The team oversees scores of researchers, activists and media professionals who promote diverse political initiatives inside Russia, investigate corruption in the Russian government and broadcast YouTube videos that attract millions of viewers in Russia every month. The movement also claims to have thousands of underground volunteers inside Russia.

In Vilnius, Navalny’s supporters have largely isolated themselves from a broader community of Russian dissidents who moved to the Lithuanian capital after Russia’s invasion of Ukraine.

They have also maintained an arms-length relationship with the government of Lithuania, which staunchly opposes Mr. Putin but views citizens of Russia, a former occupying power, with a degree of suspicion, according to two Lithuanian officials who discussed policy on the condition of anonymity.

Mr. Navalny’s team has not asked the Lithuanian state for financial support, and it has kept its distance from the country’s security services, the officials said. They explained this posture as their desire to maintain their independence and protect themselves from the Russian government.

Mr. Navalny’s team does not disclose how it pays for its operations. Its last financial report, published in 2021, showed that their movement covered three-quarters of its expenses that year with money from individual donations.

To Mr. Navalny’s supporters, his aides’ emphasis on self-sufficiency stems from years of conducting politics in a repressive state bent on destroying them. They combined the latest internet technologies with shoe leather local activism, resulting in a movement that meshes elements of a tech start-up with a 19th-century revolutionary cell.

But even some of their collaborators admit in private that the Navalny team’s insularity, confidence in their technical abilities and certainty in their course of action could cost them a unique opportunity to build a broader, more inclusive political movement that outlives its founder.

Mr. Navalny had long towered above the rest of the Russian opposition. He received 27 percent of the vote when he ran for mayor of Moscow in 2013, the only election in which he was allowed to participate. That result, his supporters say, was enough to cause the government to accelerate a campaign against Mr. Navalny, which culminated in his death in jail on Feb. 16.

Mr. Navalny’s team has long shunned the news media, preferring instead to broadcast its message through its social media channels, which include television-style news programs.

After Mr. Navalny’s death, some of his aides have given interviews to Russian journalists seen as sympathetic to their cause, but they have avoided speaking to the international news media.

The limits of the team’s go-it-alone strategy were on display in Vilnius during a rally called outside the Russian Embassy to commemorate Mr. Navalny’s death. Other opposition activists in the city said Mr. Navalny’s aides did not publicize the rally externally, and it drew a couple of dozen people.

Mr. Navalny, and later his team, long justified his aversion to political alliances by saying that his time and effort would be better spent on political activism. His unmatched political network inside Russia has meant that his team needs such alliances far less than the rest of the country’s opposition.

An outpouring of condolences for Mr. Navalny from across the Russian opposition had raised hope that his successors would try a more inclusive approach. Yet, the Navalny team quickly resumed bickering with its critics.

“Just scuttle off,” a director of Mr. Navalny’s investigative team, Ivan Zhdanov, wrote to a prominent opposition blogger, Maxim Katz, last week, in a heated exchange of messages on social media over Mr. Navalny’s burial.

Ms. Navalnaya attacked an opposition politician, Boris B. Nadezhdin, after he suggested that people could have different, even negative views of Mr. Navalny, but still support his right to a dignified burial.

“Aleksei was a hero,” Ms. Navalnaya wrote in reply to Mr. Nadezhdin, who was barred from running against Mr. Putin in the March elections. “I will not allow you to ‘have diverse opinions about him.’”