During the 1691 papal conclave, Negroni wrote a manifesto for the faction of the "zelanti" cardinals, who desired that the election of the Pope were free from nepotism and from the interferences of France, Spain and Holy Empire. In the same conclave, with compromising documents he stopped the candidature of Paluzzo Paluzzi Altieri degli Albertoni, the Cardinal-Nephew to Pope Clement X.