Striding through the Kremlin’s gold-encrusted doors and applauded by the modern nobility, Vladimir Putin returns to the Russian presidency Monday in the throne room of the czars, now a dangerously weakened autocrat.

The protests of December shook his all-powerful countenance, setting off machinations by the powers behind him who are intent on preserving their authority and privilege despite demands for democracy and reform. That conflict portends difficult and uncertain days for Russia, with Putin pressured to display more muscle than compromise.

“Putin needs to be strong,” said Vladimir Pastukhov, a Russian political scientist and visiting fellow at Oxford University, “otherwise there will be 12,000 knives to his back the next day.”

Putin has ruled Russia since 2000, the past four years as prime minister, and until December the nation had traded the unpredictability of democracy for the certainty of a strong hand.

Then, a vocal and economically important minority, angered by widespread allegations of fraud in parliamentary elections, declared an end to the bargain, taking to the streets in protest. The demonstrations shook what Putin called his “vertical of power,” based on a line of authority that ran from the Kremlin down to the smallest city hall.

By March, when he was elected president with a reported 64 percent of the vote, doubts had appeared about his legitimacy. Now, few expect anything but a long, tumultuous road for democratic reform. Many fear turmoil. No one knows what lies ahead after Monday’s inauguration for what now is a six-year presidential term.

Putin has become the protector of an army of corrupt officials and managers throughout the country who enjoy great authority and profit as long as they are loyal. Now, hidden from public view, a battle reportedly is underway between hard-liners insisting that only an uncompromising crackdown will save them and more progressive elements urging reform. The latter want to let some of the steam of anger escape and open Russia to economic development.

If Putin antagonizes the hard-liners, an assortment of security and military industrial insiders among them, he risks plots against him. If he cannot quiet the protests, he courts a popular upheaval.

Most likely, he will turn to the siloviki — the Russian term for members of the security services and military, those with power and guns — for support, said Dmitri Oreshkin, an organizer of the League of Voters, created this year to pursue fair elections.

“It probably won’t be as stringent as the Soviet Union,” he said, “but tougher than five years ago.”

On Friday, authorities in Ufa, 725 miles to the east of the capital, reportedly prevented a dozen activists from boarding a train to Moscow, where an anti-Putin demonstration is planned for Sunday. Others have reported intimidating visits from police.

“The Putin returning to the Kremlin is not the Putin who left it four years ago,” said Boris Makarenko, deputy director of the Center for Political Technologies. “He left at the peak of economic growth and optimism about increasing prosperity. Now he will be cautious, conflicted. He understands that the development of Russia and the economy requires independent actors in business and public life, but at the same time he feels the need from his KGB years to keep everything under control.”

Comparison to Gorbachev

Russians have begun to compare Putin to Mikhail Gorbachev, damning him without the faintest of praise. Many Russians despise Gorbachev, the last leader of the Soviet Union, blaming him for destroying their empire and leaving them in poverty and humiliation.

“In my opinion, Russia has entered Perestroika 2,” said Stanislav Belkovsky, director of the National Strategy Institute in Moscow. “Twenty-five years ago, Gorbachev initiated perestroika [rebuilding] because he wanted to strengthen the Communist system, not change it. But he lost control over the situation, it became turbulent, and all of Gorbachev’s reforms led to the dissolution of the Soviet Union.”

If Russia’s rulers relax their grip, they will lose power, Lilia Shevtsova, head of Russian political programs at the Carnegie Endowment for International Peace, said last month. “They’re not ready for hara-kiri,” she said, referring to the Japanese suicide ritual. “They’re looking at Gorbachev’s experience when Gorbachev’s liberalization left the elite without a state, power and the Kremlin.”

Belkovsky said that if Putin offers reforms to shore up his legitimacy, he will unleash the same kind of uncontrollable forces. Doing nothing brings its own peril, Belkovsky said, because the current system has engendered incompetent government that relies on high oil prices for survival, despite talk about diversification. Economic reversals could set the entire country against Putin.

“He believes in oil and gas, nothing more, despite what is said publicly,” Belkovsky said. “He has only one idea. As long as oil prices are high, the Russian economy survives.”

Oreshkin predicts that Putin will start running into political trouble in the fall as elections begin for local mayors and city councils. Election monitors will be vigilant and voters restive.

“They’ll have to cancel elections or lose them,” he said.

A virtual vertical of power

Putin’s vertical of power has become virtual, Oreshkin said.

“In Soviet times, they reported great harvests and cows heavy with milk,” he said, “but there was no butter in the shops. Now they say the vertical of power has brought the country up from its knees and we won’t let the Americans build their missile defense. But it means nothing, and everyone knows it.”

Now Putin must find a way to build a new system of governance, said James F. Collins, a former U.S. ambassador to Russia and director of the Carnegie Russia and Eurasia Program.

“I don’t think he can count on the vertical,” Collins said. “No one’s afraid of them anymore.”

Pastukhov and others foresee only difficult years ahead. When Putin decided to return to the presidency, brushing aside Dmitry Medvedev, who had cast himself as the liberal standard-bearer, he lost the opportunity to leave office peacefully, they say.

“He could have left Medvedev president and let Medvedev put in a compliant prime minister,” Pastukhov said. “Putin could have been a shadow dictator. Everyone would have been happy.”

But Putin’s announcement in September that he would return awakened the opposition.

That leaves Russia facing uncertainty. Mark Urnov, professor at the Higher School of Economics, noted that Putin has prevented the development of opposition politicians, and Urnov fears who might emerge if Putin and his backers fall out. A nationalist or hard-liner could appear.

“So the situation is unstable and unclear,” he said, “and the only thing I can see is that the situation will be changed. I don’t know how.”

Or when.

“The Soviet vertical lasted 70 years,” Oreshkin said. “It’s hard to say how long this one will last.”