I'm not sure exactly how to explain why I'll be at the protest," says Alan Gatsunaev, sipping green tea in a Moscow cafe.

"It just feels like I can't not be there." The 30-year-old Muscovite, wearing a grey cardigan and sporting carefully trimmed facial hair, does not look much like an angry protester. A successful real estate consultant, he has benefited from the rise in incomes and economic possibilities under the rule of Vladimir Putin over the past decade, and can invariably be found on Friday and Saturday nights sipping cocktails in upmarket Moscow nightclubs.

Before this week, he had never been to an opposition protest. But, he says, after Mr Putin announced in September that he planned to stand in March elections for a return to the presidency, he began to think enough was enough. After Sunday's parliamentary elections gave Mr Putin's United Russia party 49 per cent of the vote, despite the fact that hardly anybody he knew admitted to voting for them, he attended rallies on Monday and Tuesday night, and is one of about 35,000 who have signed up on Facebook to attend a rally in central Moscow this afternoon that will call for new elections.

"I have never thought of myself as a political person, and I think the first time I heard the name Surkov was six months ago," says Mr Gatsunaev, referring to Vladislav Surkov, a key Kremlin aide who has been the chief ideologist of Russia's political system during the rule of Mr Putin and his stop-gap replacement, Dmitry Medvedev.

"But I have changed recently. The thing that is most offensive is the level of cynicism. With the internet you can literally see that you are being lied to, and people have just lost patience."

He voted for the liberal party Yabloko at these elections, the first time he was tempted to vote since 2000, when he backed Mr Putin for election to the Kremlin for his first time. Many other urban, wealthy Russians in their 20s and 30s also voted for the first time in Sunday's elections, and are now the catalyst behind the protests.

A government-linked think tank recently estimated that the "middle class" in Russia, created during the Putin-era oil boom, now makes up 20 per cent of the population, a figure it expects to double by 2020 and provoke increased calls for political reform. But the speed with which the mood has changed has surprised almost everyone. With state television hardly making reference to the protests, and instead focussing on flag-waving celebrations by groups of pro-Putin youths, active opposition is still very much the preserve of an internet-savvy minority. But in Moscow, the change of mood among the new middle class is palpable.

"It's amazing how quickly the atmosphere in the office has changed," said one Western businessman working in Moscow. "The Russians in the office were never politicised, they never wanted to talk about politics. Suddenly, all the office conversations are about politics, everyone is debating whether or not they should go to protest. I don't think there is anyone who really hates Putin there, but it certainly seems like people have lost respect for him."

Facebook and Twitter have been alive with Russians sharing videos of alleged fraud at the elections, and Photo-shopped pictures poking fun at the country's leaders. One shows Mr Putin's face superimposed on to a photograph of ousted Libyan leader Muammar Gaddafi, while another shows a shaven headed Mr Putin and Mr Medvedev in prison overalls filling up bowls with gruel. Despite heavy handed police tactics that saw hundreds of protesters detained on Monday and Tuesday, young Russians have lost the fear and the sense that protest is hopeless that prevented more from supporting rallies in the past.

Mr Putin made no comments about the protests until Thursday, when he insisted that the whole movement had been inspired by US Secretary of State Hillary Clinton. The Americans, Mr Putin claimed, had spent "hundreds of millions of dollars" on influencing the elections in the country. Mr Medvedev has also made few significant comments on the elections, though he said that reports of voting violations should be investigated. The head of Russia's Central Election Committee, Vladimir Churov, suggested that evidence of voting fraud was filmed in apartments made to look like polling stations.

While today's turnout in Moscow, and other cities across Russia, will almost certainly make it the biggest day of protests since the Putin era began, the big question is what comes next. Those who come out today will all oppose the status quo, but only a minority will be active supporters of marginal liberal leaders such as Boris Nemtsov. Alexei Navalny, the anti-corruption blogger who was jailed for 15 days after Monday night's protest, has the first beginnings of real grassroots support, but no real political experience.

As if to reinforce claims that the opposition is fractious and disorganised, several of its leaders had its own "People's Front of Judea" moment late on Thursday, as they argued over whether to hold the Moscow protest as initially planned on Revolution Square, where authorities said that only 300 people could meet and others would be arrested, or move it to the less symbolic Bolotnaya Square, where the Moscow mayoralty has said up 30,000 people can meet. Agreement was reached only after a vitriolic bout of name-calling.

Permission for such a large meeting of anti-government forces is unheard of in recent Russian history, and suggests that Mr Putin may be attempting to show the world he can accept some carefully managed dissent.

But separately, authorities have gone out of their way to disrupt today's protest. Rumours circulated online that young men at the rally would be stopped by police and could be conscripted into the army on the spot, while the country's top health official warned Russians they should stay at home or risk contracting flu or Sars. Twitter feeds were flooded with spam messages, while Yabloko's headquarters began receiving phonecalls from a female-voiced robot, saying "Putin loves you", "Putin will open your eyes", and "Love Putin and your life will have meaning".

The calls came so frequently that it was impossible to work. The Moscow authorities also designated today a school day for older classes, presumably to ensure that the pupils were unable to attend the rally.

Despite all of this, thousands are expected to come out on to the streets today. "I think the main impulse to go is to tell the government that we don't want to be treated like idiots any more," said graphic designer Anna Zorina, 24, who has not attended a protest before.

Mr Gatsunaev said that if the protests continued until March, they could send a real message to Mr Putin ahead of presidential elections: "People are offended. They feel like they are being spat on from a height, and the people in charge have forgotten that we put them there. It's like when somebody steals your woman, you just feel obliged to defend her. Right now it feels like Russia has been stolen from us."

Timeline: The week that changed Russia

Sunday

Parliamentary elections across the country. Overnight, Vladimir Putin's United Russia party is announced as the winner, with 49 per cent of the vote, down from 64 per cent in 2007.

Monday

Hundreds of videos uploaded to YouTube supposedly showing violations at polling stations. A planned rally in central Moscow organised by democratic opposition draws unprecedented crowd of around 8,000. There are mass arrests when protestors try to march towards the FSB headquarters, Lubyanka.

Tuesday

Two opposition leaders, Alexei Navalny, below left, and Ilya Yashin, below right, are jailed for 15 days. Crowds mass again on Triumfalnaya Square, this time faced off by members of Nashi, the pro-Putin youth group. More than 500 protesters are arrested.

Wednesday

Protesters announce massive meetings for Saturday in cities across Russia. The Moscow meeting threatens to become one of the biggest in modern Russian history. A small group of protesters rallies at Triumfalnaya again.

Thursday

Vladimir Putin accuses the US and Hillary Clinton of stoking the protests. Moscow authorities offer opposition a different square from the one they wanted in which to hold their rally. Opposition leaders begin to argue.

Friday