Voting began on Sunday in Moscow's mayoral election with incumbent Sergei Sobyanin, who is backed by President Vladimir Putin, expected to win easily.
However the entry of charismatic opposition figure Aleksei Navalny has added an element of uncertainty unseen in Russian elections since Putin's rise to power.
His candidacy has sparked the formation of one of Russia's first-ever grassroots campaigns and is one of the first times in a decade that Muscovites have been offered a real choice on the ballot.
If Navalny can get more than 20 per cent and even come close to forcing incumbent Sergei Sobyanin into a runoff, it could embolden the downtrodden grassroots opposition in its efforts to thwart Putin.
A vote seen as unfair could trigger more protests against the government.
Navalny takes anti-corruption stand
Navalny started an anti-corruption blog in 2009, and used his status as a minority stakeholder in state-owned companies to expose corruption, most famously uncovering a four billion dollar theft by oil pipeline operator Transneft.
His charisma and cutting wit turned him into an online folk hero of the opposition, and he soon began taking a stance on broader political issues, coining the nickname for Kremlin-backed United Russia as the "party of crooks and thieves."
When unprecedented protests broke out after 2011 parliamentary elections that were widely reported to be rigged, Navalny cemented his status as de facto leader of the opposition, leading street marches that attracted hundreds of thousands of people from all ends of the political spectrum.
Navalny was sentenced to five years in prison for embezzlement in July and left the trial in handcuffs. But a day later in a surprise turnaround, prosecutors requested he be set free until the decision was approved on appeal.
Most have speculated that it was Sobyanin who had Navalny set free, in order to ensure that the elections would look as fair as possible and legitimise himself as a politician.
Sobyanin started his political career in the oil-rich Siberian town of Tyumen, but quickly moved up the political hierarchy to work as an aide in the Kremlin.
He was parachuted into the seat of Moscow mayor in 2010 after the charismatic Yuri Luzhkov, who governed the city for almost two decades, was forced out.
Sobyanin is most popular among the pensioners who rely on his office for hand-outs, but he has gained respect for directing the city's $54-billion budget toward the city's parks and cultural institutions.
Sobyanin has relied on his financial advantage and political backing to run his campaign for him, and has mostly played the regal and removed incumbent who has refused to participate in debates and appears only rarely in stage-crafted public events.
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