The murder of the Brazilian councilwoman Marielle Franco in March 2018 was an event that mobilized diverse individuals throughout Brazil as well as in various parts of the world. Digital social networks played a fundamental role in promoting the visibility and repercussion of the case as data, narratives, and emotions circulated. Having as a source virtual records on Twitter between the months of March 2018 and March 2019 we propose to reflect on the role played by the network in this process, more specifically how the emotions were propagated by the death of the parliamentarian. The power of the affective contagion (SAMPSON, 2012) of a digital commotion is not only a mere manifestation among users of a platform but also - due to the action of the algorithms target of increasingly affective capitalism and of great political strategies of ideological dispute. Our reflection is also marked by the disruptive role that emerged in this event in a scenario of the rise of conservatism in Brazil and the organization of a right arising from political opportunity opened by social networks. We will use authors like Gabriel Tarde (2007, 2011a, 2011b), Tony Sampson (2012) and Byung-Chul Han (2016, 2017, 2018) to analyze the contagion of ideas in society and how virality is constituted in the capitalism of emotion, and also to Esther Solano (2018) and Velasco e Cruz, Kaysel and Codas (2015) to understand the contemporary Brazilian political scene.