He's a bare-knuckled street brawler. He's a firebrand leftist. And he's an unapologetic Stalinist who wants to restore the Soviet Union.
For nearly five years, Sergei Udaltsov has been Russia's most invisible political prisoner.
The public didn't read his prison letters. Rights groups didn't take up his cause. He didn't become a media star.
But with his release from prison last week, Udaltsov has suddenly become an important political barometer.
Because as soon as Udaltsov walked free, the rumors, the speculation, and the innuendo swirled that he had cut a deal with the Kremlin: that in exchange for his freedom he had agreed to be co-opted by the system and play the role of the spoiler.
Now, we don't know how much credence to give this speculation, but it would certainly fit the Kremlin's playbook -- and its political needs of the moment.
Vladimir Putin's regime fears the antiestablishment mood that opposition leader Aleksei Navalny has so effectively and skilfully tapped into. And it fears the politically active and nonconformist youth.
And what better way to neutralize this threat than to use a streetwise leftist firebrand to divide it, to turn Udaltsov into a housebroken anti-Navalny.
In his initial comments after his release, Udaltsov seemed to play the role. He criticized Navalny and expressed support for the annexation of Crimea and the war in the Donbas.
But as opposition journalist Oleg Kashin wrote in a recent column, the role of Kremlin patsy doesn't really suit the fiercely ideological Udaltsov.
For five years, Udaltsov has been the Russian opposition's invisible man. But what he does now has suddenly become very consequential.