Vladimir Putin the Russian opposition and by international observers from the Organization for Security and Co-operation in Europe for procedural irregularities. Anti-Putin protests took place during and directly after the presidential campaign. The most notorious protest was the Pussy Riot performance on 21 February, and subsequent trial. An estimated 8,000–20,000 protesters gathered in Moscow on 6 May, when eighty people were injured in confrontations with police, and 450 were arrested, with another 120 arrests taking place the following day. A counter-protest of Putin supporters occurred which culminated in a gathering of an estimated 130,000 supporters at the Luzhniki Stadium, Russia's largest stadium.
Vladimir Putin presidential campaign, 2012 did not exclude that he will participate in the 2012 election. On 24 September 2011, at the United Russia party convention for the legislative elections, Medvedev announced that he would not seek re-election, and suggested that Vladimir Putin run for President again. On the same day, Putin announced his participation in the elections. On 27 November 2011, Luzhniki Stadium hosted the pre-election Conventon of the United Russia. In total, the Conventon was attended by 11 thousand participants, of which only 614 had the right to vote. Vladimir Putin was unanimously nominated as a presidential candidate from the United Russia. On