MOSCOW -- In closing arguments on Friday, prosecutors urged a Russian judge to convict the political opposition leader Aleksei A. Navalny of embezzlement and sentence him to six years in jail -- a verdict that would destroy his political career and eliminate him as a threat to President Vladimir V. Putin by imprisoning him until after the next presidential election.
Mr. Navalny is the most prominent opposition figure in modern Russia to face prosecution, and he has accused the Kremlin of pursuing trumped-up charges as political retribution. While forcefully denying the allegations, he has long said he expects to be convicted in the trial, which was streamed live online from Kirov, a regional capital. The verdict is to be delivered on July 18.
For more than a year, as Mr. Navalny helped to lead big street protests against Mr. Putin, the Kremlin seemed to waver between a desire to imprison him and a reluctance to galvanize his supporters by locking him up. Mr. Navalny has declared his candidacy for mayor of Moscow in an election to be held in September, but he has also said he hopes one day to be president.
"Change Russia," proclaims a glossy pamphlet produced by his campaign. "Start with Moscow." It adds the tag line, "Honest leadership -- a European level of life."
This particular case against Mr. Navalny -- he faces several others -- stems from a brief period when he served as an adviser to the governor of the Kirov region, where his work included efforts to reorganize a government-controlled timber company. Mr. Navalny and a co-defendant are charged with embezzling nearly $500,000 from the company. A third man accused in the scheme pleaded guilty and has cooperated with the prosecutors.
If Mr. Navalny, 37, is convicted of criminal charges, he will be barred from running for mayor or any other office. A six-year jail term, while less than the maximum possible sentence of 10 years, would, if served in full, keep him in prison until after Russia's next presidential election in 2018.
In addition to the six-year jail term, the prosecutor, Sergei Bogdanov, asked the judge to impose a fine of about $30,000. "I believe that the punishment proposed by the state is just and proportionate to the committed crime and the loss suffered by the state," Mr. Bogdanov said.
Mr. Navalny rose to prominence as an anticorruption blogger with a special knack for turning a scathing phrase. The most devastating was his branding of United Russia, which supported Mr. Putin for president, as "the party of swindlers and thieves" -- which quickly became an unshakable catchphrase.
In a defiant speech in the courtroom on Friday, Mr. Navalny, wearing khaki slacks and a white dress shirt with the sleeves rolled up, denounced the Russian government, and pledged to push ahead with his opposition activities.
"Myself and my colleagues will do everything possible to destroy this feudal regime being established in Russia," he said. "If somebody thinks that having heard the threat of the six-year imprisonment I would run away abroad or hide somewhere, they are mistaken. I cannot run away from myself. I have nothing else but this, and I don't want to do anything else but to help my country."
He added, "This cannot last endlessly, that the 140-million-strong people of one of the biggest and richest countries are subjugated to a handful of bastards."
In the mayoral race, Mr. Navalny is challenging the popular and heavily favored, Kremlin-backed incumbent, Sergei S. Sobyanin, who submitted his resignation this year in a maneuver to call early elections.
The risk of inciting Mr. Navalny's supporters, and bolstering his stature as a rival of Mr. Putin, has prompted speculation that he will receive a suspended sentence. That would still end his political aspirations, however.
The Kremlin has insisted that it does not interfere in the workings of the justice system. But Mr. Navalny is just one of several opposition leaders now facing criminal charges seemingly unrelated to their political activity. Acquittals in Russian criminal cases are extremely rare.
The allegations against Mr. Navalny were originally investigated in Kirov and dropped by the local authorities, who said there was insufficient evidence of a crime. But the case was revived after being taken over by the federal Investigative Committee, which is led by Aleksandr I. Bastrykin, a close ally of President Putin.
Mr. Navalny has lived with the risk of being arrested for years, and has served several short-term detentions, typically after his arrest at street protests. In recent months, however, the authorities have barred him from traveling abroad.
In the courtroom on Friday, one of Mr. Navalny's lawyers, Olga Mikhailova, repeated the defense team's denunciation of the case as politically motivated and unjust. "The character of the charges, the lack of real evidence from the prosecution, the judge's dismissal of nearly all defense motions all bear witness that this trial does not answer to the rules of justice," she said, "and is aimed at only one thing: to publicly discredit and sentence a famous civic and political activist for political motives."
Mr. Bogdanov sought to portray the case as routine, with the notable exception of its celebrity defendant. "There are a great number of similar crimes, and there is nothing new in our criminal case, not in the goals, nor the means, nor the execution of the crime," he said. "There is only one difference: the accused. It is he who evokes genuine interest in society and adds a special resonance to the case."
Mr. Bogdanov accused the public and the news media of misrepresenting the facts of the case. "There is nothing worse for justice than when a decision of the court is preceded by the opinion of the public," he said.
This article originally appeared in The New York Times.