This is informative https://politics.stackexchange.com/a/27658/25206

tl;dr Other parties are Putin-like, and if/when a genuine alternative emerges, Putin deals with them ruthlessly. Example: Navalny was the charismatic leader of a small but popular rival party with anti-corruption policies. He was initially delegitimised (not allowed to partake in the 2018 elections due to [likely fake] charges of embezzlement), then poisoned (nearly died), then imprisoned, and then killed while in prison.

Consider the terrifying message that sends to would-be political rivals...