MOSCOW — He can’t walk and can barely move his hands, but thanks to his sharp mind, a working finger and a red iPhone attached to his wheelchair, Aleksandr Gorbunov now ranks as one of the Kremlin’s most potent foes.

Mixing dark humor with sardonic analysis of Russia’s direction under President Vladimir V. Putin, Mr. Gorbunov, 27, has become a social media sensation, outpacing Kremlin propagandists in the race for attention on Twitter, Instagram and Telegram, a secure messaging service developed by Russians that Moscow tried in vain last year to shut down.

He has 1.1 million followers on Twitter — twice as many as Margarita Simonyan, the head of Kremlin-funded RT television. Alexei Navalny, the anti-corruption campaigner, has described him as the country’s “most important political commentator.” That, Mr. Navalny said, is a “funny and cool fact.”

Mr. Gorbunov has spinal muscular atrophy, a degenerative genetic disease for which there is no cure, though some expensive and risky new gene therapy treatments offer some hope.