A fissure in the foundation of Prime Minister Vladimir Putin’s political fortress that developed, barely visible, in September has widened noticeably on the eve of Sunday’s parliamentary elections.

Political scientists say a too-heavy Kremlin hand has not only alienated ordinary citizens but also threatened the country’s stability, which depends on Putin’s popularity rather than poorly developed national institutions. The dissonance has been amplified by Russia’s spirited Internet, which provides a forum for opposition that the authorities have found difficult to manage.

Officials struck back this week, going after the country’s only independent election monitoring organization, Golos, which has been operating an online map tracking campaign violations across the country. A court found it guilty Friday night of violating a law forbidding publication of public-opinion reports close to an election and imposed a fine equivalent to about $1,000. Early Saturday, Golos leader Lilya Shibanova was detained at Moscow’s Sheremetyevo airport for 12 hours and was allowed to go only after giving her laptop to security officers, the group said.

“Golos has become a most important and respected monitor,” said Oleg Kozyrev, a media analyst and influential blogger. “The authorities were afraid people would learn the truth about how elections are manipulated.”

But the public mood had already changed, and it was reverberating through the blogosphere. Reports of the attack on Golos were quickly met with a rap song ridiculing the tactics, lighting up the online world. The chatter turned to voting against the dominant United Russia party rather than ignoring the elections as useless.

“An accumulation of incremental events has turned into an enormous wave of negative emotion,” said Mark Urnov, dean of political studies at the Higher School of Economics, and the authorities don’t understand how to adapt. “That is why they reacted so badly to Golos and made a mistake.”

The Kremlin began losing its footing, Kozyrev said, in mid-September. To offer the appearance of choice, Mikhail Prokhorov, the billionaire owner of the New Jersey Nets, had been persuaded to take over the leadership of the moribund Right Cause party. He quickly became too independent, and the authorities made a messy job of throwing him out.

Although it was clear the party would not offer real opposition — the Kremlin prohibits that — Prokhorov was popular with businessmen, and he gave them some room to maneuver politically. His ouster ended up alienating a constituency loyal to the power structure, Kozyrev said.

Then, just over a week later, President Dmitry Medvedev told a cheering United Russia congress that he would step aside for Putin to run in the March presidential election. “The middle class reacted quite strongly after that,” Urnov said. “They thought Medvedev could be a leader representing their hopes. Now his popularity is annihilated.”

Putin’s popularity began to drop, as did United Russia’s. Although polls predict that the party will win 53 percent of the vote Sunday, numbers short of the 64.3 percent it received in 2007 are viewed as unacceptably weak.

“The dropping of his popularity is a signal to regional leaders that they can act more freely,” Urnov said, suggesting dangerous possibilities in a country that relies on Putin’s power for stability.

The Internet ferment has drawn in young voters, considered until now an apathetic generation, and government policies have been alienating them. Indira Valeyeva, a 21-year-old student at Moscow State University from the city of Ufa, said students have always been automatically registered to vote when their Moscow residency was recorded. This year, the policy was changed with little publicity.

When she went to register Wednesday, the line was so long that she was not registered when the office closed, and the students were told to leave.

“At first, I didn’t want to vote,” she said. “I heard everyone saying, ‘Why vote when we can’t change anything.’ But I began thinking that if we all stay away, it’s certain nothing will change.”

Her change of heart began in September. “They made it clear they didn’t respect our opinions,” Valeyeva said, “and it made us want to do something.”

Critics of the authorities fear that roadblocks are being put in the way of students so their votes can be stolen, among a host of other potential violations. On Friday night, Golos officials said they expected to be watching Sunday, despite the rigorous campaign against them.

The main evidence against them came from Vladimir Churov, head of the Central Election Commission, who complained that the violations Golos was reporting mostly centered on United Russia, which would create a negative impression of the party.

Churov once told a newspaper that his first rule was “Putin is always right.”

Within an hour after the court decision, the NTV channel owned by a Putin ally broadcast a smear against Golos, using images of suitcases stuffed with hundred-dollar bills to illustrate its accusation that the United States was paying Golos to distort the election.

Despite all the emotion, observers say United Russia will prevail and the streets will remain free of angry protest.

“The limits of dissatisfaction have not yet been reached,” Kozyrev said. “There are no political forces or leaders capable of using it.”