Profile: Alexei Navalny, Russian opposition leader
30 October 2012 Last updated at 18:41 GMT
The Russian lawyer and anti-corruption campaigner Alexei Navalny recently topped a ballot to elect leaders of the opposition to President Putin.
Lucy Ash profiles the man who came to prominence as a leader during the anti-Putin demonstrations in Moscow last December - the biggest such rallies since the end of the Soviet Union.
Navalny has also been fighting against corruption through a website that invites the public to report suspected cases to the police or prosecutors. One of his tactics was to become a minority shareholder in major Russian oil companies, banks, and ministries to ask awkward questions about holes in state finances - and those holes are huge.
Last year Dmitri Medvedev - then President, now Prime Minister - said that a trillion roubles ($33 billion) disappears annually on government contracts. Navalny's campaign has won him popularity across a wide spectrum of Russian society - including nationalists with far-right connections, and this has unsettled many more liberal supporters.
And in a week when three other opposition activists have been charged with causing mass unrest, does Alexei Navalny have what it takes to challenge the tough man in the Kremlin?