Q&A: Russia's presidential election

Not since the 1990s has a Russian presidential election attracted as much interest and intrigue as the vote taking place this Sunday.

The run-up to the election has been marked by opposition protests and a surge of opposition activism sparked by Vladimir Putin's return to stand for a third term after four years as prime minister, as well as allegations of electoral fraud in last December's parliamentary elections.

The winning candidate must receive more than 50% of the vote. If there is no outright victor, the two leading candidates go through to a run-off.

Apart from Mr Putin, four other candidates are standing: Communist Party leader Gennady Zyuganov, nationalist Vladimir Zhirinovsky, the leader of the Just Russia party, Sergei Mironov, and millionaire businessman Mikhail Prokhorov.

Despite suggestions that his popularity may be waning, recent opinion polls give Mr Putin a solid lead with around 50% of vote. Nevertheless, this is some way off the 71% he won in his last presidential election in 2004.

Of the other candidates, only Mr Zyuganov and Mr Zhirinovsky have shown signs of even coming close to double percentage figures, and none of the candidates is seen as representing the street protest movement against Mr Putin.

While Mr Putin is still expected to win with relative ease, the vote is seen as a referendum on his 12 years of nearly unchallenged domination of Russian politics.

After two four-year terms as president, he ceded the office to close ally Dmitry Medvedev in 2006 and became prime minister, but is widely thought to have retained overall control.

News in 2011 that he would be standing for a third term was received with dissatisfaction among some Russians, especially the new urban middle class increasingly chafing at widespread corruption.

The anger boiled over following allegations of widespread vote-rigging in parliamentary elections in December, with Moscow witnessing opposition protests not seen since the collapse of the Soviet Union.

Mr Putin has fought back, presenting himself as the man who saved Russia from the instability of the 1990s and restored it to the status of global power, able to resist what he frequently depicts as the West's plans for hegemony.

While the protest movement may have only slightly dented Putin's standing with most Russians, they have galvanised efforts by civil society groups and anti-Putin campaigners to scrutinise the conduct of the election.

Two main independent monitoring groups have sprung up with the aim of recruiting volunteer monitors - the League of Voters, which was founded in January by a group of public figures who played a prominent part in the December protests, and Rosvybory, which is run by blogger and anti-corruption campaigner Alexei Navalny.

Both groups are cooperating with older organisations that monitored December's parliamentary election, including Golos ("Vote" or "Voice"), Russia's oldest independent election monitoring group. The methods being used to attract volunteers include glossy YouTube videos, and even a smartphone app.

The main response has been an order by Mr Putin for cameras to be installed at all of Russia's 96,000 polling stations. The Central Election Commission followed this up with an order to polling station heads to show every page of their electoral return to the cameras.

But critics say there is no guarantee that there will be sufficient bandwidth to view the footage or that opposition observers will be given access to footage.

While the new monitoring groups have had a relatively tolerant response from the authorities, Golos claims that it is being harassed on the government's orders, to the extent of having been kicked out of its offices without explanation.

With opposition activists estimating fraud to have made a difference of as much as 15% to the December parliamentary vote, some observers say the unprecedented number of monitors could have an impact on the conduct of the election.

However, there are also doubts about the monitors' effectiveness. While in theory they can freely move around polling stations, they have in practice often been obstructed and even ejected from polling stations in the past.

Observers also caution that most independent monitors will be concentrated in large urban areas, leaving the election lightly monitored in much of the rest of Russia's vast territory.

As in the past, Mr Putin can count on the enthusiastic backing of the tightly-controlled main national state television channels. Only some smaller private TV stations are likely to deviate from this line, but their reach is limited to a small number of urban areas.

Recent state TV coverage has continued its traditional pattern of portraying Mr Putin as a strong, masculine leader capable of defending Russian national interests at home and abroad.

Since the December elections, the state TV channels have softened their usual disregard for critical voices, with several anti-establishment politicians being allowed to appear after years of absence.

However, this has coincided with growing pressure from the authorities on the handful of outlets of free speech in Russia, including liberal radio station Ekho Moskvy and the outspoken newspaper Novaya Gazeta.

Mr Putin also angered opponents by refusing to take part in planned TV debates between the candidates, saying his duties as prime minister made it impractical for him to attend, and that he would send representatives instead. One opposition spokesman said the move showed "disrespect" to his opponents.

While television - still the main news medium for most Russians - may still largely favour Mr Putin, the internet is a growing factor. With little government regulation, opposition voices have a strong presence on the web, and the internet has been one of the driving forces behind the anti-Putin protests.

BBC Monitoring selects and translates news from radio, television, press, news agencies and the internet from 150 countries in more than 70 languages. It is based in Caversham, UK, and has several bureaux abroad.