This contribution explores the tension between Petrarch's affiliation with the Florentine literary tradition and his broader transregional influence by examining the commentaries of Francesco Filelfo and Francesco Patrizi da Siena on the Rerum vulgarium fragmenta. While Cristoforo Landino's Proemio al commento dantesco (1481) presents Petrarch as a central figure in the refinement of the Florentine vernacular, his reception outside Florence — particularly in Milan and Naples — reveals a more complex dynamic. Drawing on Alexander Beecroft's framework of literary circulation, and Gianfranco Contini’s notion of "fiorentinità trascendentale", the study investigates how Petrarch's language and authorship oscillate between a localized identity for the Florentine community and a transregional legacy claimed by a vernacular cultural community. By analyzing linguistic and political constraints, such as the competition between Milan and Florence and the role of Latin in vernacular literary culture, this chapter illuminates the broader stakes of Petrarch’s canonization in the fifteenth and sixteenth century.