The decline in Vladimir Putin's popularity can be dated very precisely. It began on September 24 last year when he persuaded his junior partner in power, the current president, Dmitry Medvedev, to stand up and propose him as the next master of the Kremlin.
Such a move was hardly unexpected. Mr Medvedev had been a placeholder for Mr Putin who, having served two terms in the Kremlin, was barred by the constitution from a third consecutive term. The pair were memorably described in a US embassy cable as the Batman and Robin of Russian politics, and it was clear to all who the senior partner was.
But the rough manner of Mr Putin's sweeping his partner aside awoke broad sections of the Russian middle classes - they might call themselves the intelligentsia - from their political torpor. It seemed like a putsch, and so out of tune with the spirit set by the popular rebellions of the Arab Spring.
Mr Putin's aura as a Tsar-like figure above politics was damaged. Instead, he appeared as the protector of an immovable bureaucratic and business elite growing fat on the Russian state.
Mr Putin was heckled in public, and the elections for the Duma, the Russian parliament, in December were - thanks to an electorate armed with smartphones - so obviously rigged in favour of Mr Putin's party, United Russia, that mass protests erupted in Moscow.
The 2011-12 electoral cycle comes to an end on Sunday with the presidential election, and it is unthinkable that Mr Putin will fail to win on the first round. There are no convincing opponents, and the real issue will be how many people bother to vote, and whether it is possible for Mr Putin to achieve a convincing victory without obvious vote rigging.
What should have been a chance to renew the leadership will thus turn into a new lease for the old regime that could give Mr Putin a further 12 years in power.
Protests in Russia focus on Mr Putin personally. Demonstrators began by carrying digitally altered placards showing a haggard Mr Putin as he might look in 2024. More recently, digital activists have turned the idea on its head: Mr Putin, whose smooth forehead has prompted suggestions he uses Botox, is shown looking spookily younger as the years go by.
His declining popularity should not be exaggerated. He has a solid base of support among old people, who see him as the best guarantor of their pensions, and those who work in state enterprises which, under a reformist leader, could all go bankrupt.
According to polling by the Levada Centre, less than one quarter of Russians favour US or European-style democracy. Forty-five per cent want a form of democracy that responds to the "national traditions and characteristics of Russia" - presumably autocracy under the Tsars and one-party rule under the communists.
Given that Russia will have Mr Putin as president again, the question is how long can he keep a failing system running. Russia is not bankrupt - indeed its growth rate and public finances are blossoming, compared with those of debt-laden western Europe.
But that is because of an oil price of over $100 a barrel. If the price falls, say because of a worldwide recession, to $60 a barrel, then confidence in the economy would collapse, according to Philip Hanson, emeritus professor of the political economy of Russia at the University of Birmingham in the UK.
At the same time, Mr Putin's big- power ambitions are leading him to invest heavily in Russia's military rather than bringing it down to a more manageable size befitting Russia's role in the world. Spending on national defence, state security and law enforcement are all due to rise, to the detriment of health and education. These budgetary priorities suggest Mr Putin is well aware of the challenge he faces and is building up his security forces in case the so-far peaceful street protests grow more violent, or spread to provincial cities.
The consensus among experts is that this election signals the beginning of the end of the Putin system. Few, however, are willing to put a time limit on his power. The chances of him serving out two six-year terms are slim, but his ability to co-opt his opponents should not be underestimated.
What is certain is that domestic concerns will colour his assessment of events in the Arab world and beyond. For him the Arab Spring is a sign not of a yearning for democracy, but of a rising tide of violence in the world, promoted by the US for its own commercial ends and leading to an uncertain future most likely dominated by radical Islam.
For Mr Putin, it is logical for the Syrian regime to massacre the opposition just as the Russian army crushed the Chechen separatists, the conflict which sealed Mr Putin's rise to power.
Given the continuing instability of Chechnya and neighbouring Muslim lands of Russia's North Caucasus region, it is easy for Mr Putin to scare his electorate with the message that change means disorder on the scale of Syria or Libya.
But on the global stage, it looks like Mr Putin is backing the wrong side. A more nuanced approach to the Syrian crisis would have promoted Russia's claims to be a power broker in the Middle East. Now Mr Putin looks like an angry man shouting from the sidelines.
The harsh tone that he is adopting towards the US is unlikely to be just a feature of the election campaign. Such tough talk is popular in Russia, and will no doubt be central to his new presidency. As for western powers, there is not much they can do but to accept him as president. They will know, however, that his lease on power is not endless and that the Russian people will have the final say.
Follow on Twitter: @aphilps