Despite its ever-present and at times escalating significance, conspiracy theory is an under-researched topic in the social sciences. This paper analyses the political influence of conspiracy theories by drawing on semi-structured interviews with the representatives of four major political parties from the Turkish parliament about widespread anti-Semitic conspiracy theories regarding Dönmes (converts). The findings indicate that right-wing political parties problematize the secret character of the Dönme community and use the conspiracy theories to express their own ontological insecurities emerging from the Sèvres syndrome. Left-wing and liberal parties conversely dissociate themselves from the conspiratorial rhetoric. The research concludes that the political parties reject or accept the conspiracy theories rationally and in alignment with their own ontological insecurities; by doing so, they pragmatically confirm their individual ideological perspective.