Thousands gather in Russia's two biggest cities to call for change.
Many here want to see Vladimir Putin's ruling party - United Russia - nullify recent parliamentary elections results they say favored its candidates unfairly.
Leaders from the opposition are hoping to capitalize on long brewing anti-government sentiments.
(SOUNDBITE) (Russian) ' A JUST RUSSIA ' LEADER SERGEI MIRONOV ADDRESSING RALLY SAYING
"The new election law must dismiss the current Duma and call new elections because the Duma and the Federation Council should serve the people and people must trust those who sit there do so with a legal mandate and not as a result of faslifications. This is our position - that of the 'A Just Russia' party and mine too, Sergei Mironov, presidential candidate of 'A Just Russia.' Justice will win."
Their supporters, who are growing in number, say Russian politics is rife with corruption and propaganda.
(SOUNDBITE) (Russian) PROTESTER DARIA, SAYING:
"The election that we had recently for the State Duma. I don't like that our authorities, that is that man and that man are openly and unashamedly lying to the people, lying to the Internet community which sees everything. You can show everything on TV, but we see the reality."
United Russia barely managed to hang on to a majority in parliament, the biggest blow to the party since it came into power in 1999.
Jessica Gray, Reuters