He decided the cash “was for a good cause” — halting the spread of NATO and capitalist Western ways into the formerly communist lands of Eastern Europe — so he accepted.

The strange relationship that followed, consisting of passionate social media exchanges about politics and a total of €1,500 in cash transfers, was one of many forged across Eastern and Central Europe in summer 2014. They were part of a frenetic, though often clumsy, influence campaign financed from Moscow and directed by Alexander Usovsky, a Belarus-born writer, Russian-nationalist agitator and ideological hired gun in a shadowy battle for hearts and minds between Russia and the West.

Compared with Russia’s supposed meddling in the recent presidential elections in France and the United States, the activities of Mr. Kasuka and those like him are of little consequence. He belongs firmly to the fringe of Czech politics, and has never aspired to any higher office than local councilor in Melnik, the town north of Prague where he lives with his girlfriend in a graffiti-smeared housing block.

Mr. Kasuka’s collaboration with Mr. Usovsky first came to light in a cache of emails, Facebook messages and other data pilfered by Ukrainian hackers from Mr. Usovsky’s computer. It provides a rare ground-level view of a particularly murky aspect of Russia’s influence strategy: freelance activists who promote its agenda abroad, but get their backing from Russian tycoons and others close to the Kremlin, not the Russian state itself.

Mr. Usovsky’s focus was on marginal political players in the Czech Republic, Hungary, Poland and Slovakia, and his efforts mostly fell flat. The protests organized by Mr. Kasuka and others attracted only handfuls of people. Pro-Russian websites that Mr. Usovsky helped to set up all fizzled. A Polish politician he was in touch with, Mateusz Piskorski, was arrested last year on suspicion of spying for Russia.