The success of the Italian party Five Star Movement (M5S) has been broadly attributed to its ability to occupy the space of radical protest against "old politics". Due to the party’s criticism, its charismatic leadership, and its aggressive electoral campaigns, the M5S has been labeled as a populist. The unexpected result of 2013 election raises crucial theoretical questions: To what extent does the M5S electorate reflect the characteristics of a protest vote? To what extent was it also a vote driven by values, by individual evaluations on a specific political issue? The first part of the article aims to investigate the extent of negative political feelings among M5S’ voters. To disentangle the meaning and impact of protest, we distinguish two dimensions: the "system discontent" and the "élite discontent," referring to both general and focalized images, sentiments toward and the representation of political institutions, voter power, and government performances. In the second part, we bring to the analysis a further explanation based on the theory of issue voting. The goal is to measure whether voters have chosen M5S purely because of their political resentment or also given that they shared a similar position on a number of crucial policies emphasized in the electoral campaign.