Alexey Navalny

He has called Mr Putin's party a place of "crooks and thieves", accused the president's system of "sucking the blood out of Russia" and vowed to destroy the "feudal state" being built. He has led nationwide protests against the authorities. But he has not been able to fulfil what is, perhaps, his biggest dream: challenge Mr Putin in the ballot box. His candidacy in the 2018 presidential election was banned by authorities over his conviction by a Russian court of embezzlement, which bars him from running for office. Mr Navalny vehemently denies the accusations, saying his legal troubles are Kremlin reprisals for his fierce criticism.