Because they are marginalized by Kremlin’s controlled media. In their parliament “Duma”, Putin hasn’t have real opposition. Communist and nationalist only pretend that are.
Mr. Kasparov started his political career not so long time ago. But liberals (Khakamada, Nemtsov, Yavlinsky) have already lost any popular confidence. His ideas are unpopular that's why he's marginal whether the Kremlin controls Russian media or not.
Moreover, a half-Jew from Azeri city of Baku has no chances for President's office in Russia in any circumstances.
"Because they are marginalized by Kremlin’s controlled media."
Agreed. If someone in the legislature really got going, they would be killed by "gangsters" and there would be no apparent police investigation, no suspects, and no arrests. Just like what happens to prominent reporters.
I wonder what the "FR Putin-Lovers" think of that?