After the programme was agreed, however, a clash arose between Marx and his French supporters arose over the purpose of the minimum section. Whereas Marx saw this as a practical means of agitation around demands that were achievable within the framework of capitalism, Guesde took a very different view: “Discounting the possibility of obtaining these reforms from the bourgeoisie, Guesde regarded them not as a practical programme of struggle, but simply ... as bait with which to lure the workers from Radicalism.” The rejection of these reforms would, Guesde believed, “free the proletariat of its last reformist illusions and convince it of the impossibility of avoiding a workers ’89.” Accusing Guesde and Lafargue of “revolutionary phrase-mongering” and of denying the value of reformist struggles, Marx made his famous remark that, if their politics represented Marxism, “ce qu'il y a de certain c'est que moi, je ne suis pas Marxiste” (“what is certain is that I myself am not a Marxist”).

Source: https://www.marxists.org/archive/marx/works/1880/05/parti-ouvrier.htm