One of the Kremlin's most vocal critics, Alexei Navalny, has said he will stand for the Russian presidency in 2018.
The activist and anti-corruption campaigner said those in power had stopped listening to criticism.
He won more than a quarter of the vote when he stood for Moscow mayor in 2013.
Mr Navalny accuses Russian officials of trying to keep him out of the race by putting him on trial for a second time on embezzlement charges.
Last month, Russia's supreme court ordered the retrial after the European Court of Human Rights (ECHR) ruled that Mr Navalny's right to a fair trial had been violated in a 2013 case in which "criminal law had been arbitrarily construed to the applicants' detriment". A further conviction would disqualify him from standing.
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President Vladimir Putin has not yet decided whether to run for the presidency for a fourth term.
Although Russia's constitution only allows two consecutive terms, Mr Putin served from 2000-2008 before becoming prime minister and returning as president in 2012 for a longer six-year term.
If he stands again and wins, he will serve until 2024. His approval rating is running at 86% according to independent pollster Levada.
"Those in power have been there for 17 years and they've stopped reacting to any criticism," Mr Navalny said in a video statement (in Russian), adding that it was important that there was a "clash of ideas" in an election, and a real choice.
The opposition activist has had considerable success as a blogger, launching a video investigation on YouTube a year ago that included detailed allegations of corruption. The video has attracted more than five million views.