This work analyses the political communication campaign that developed following the Sienese conspiracy of 1456. The aim is to show how the political factions in power in Siena during the Renaissance continued to use the political culture of the Buon Governo [Good Governance] to legitimise their authority and gain broad popular consensus. In this case, the new government even succeeded in legitimising the closure of the political situation and establishing a temporary oligarchic season with the use of political communication based entirely on the civic symbols and languages of the bonum commune [common good].