Turnout has decreased in 23 out of 36 established democracies since 1945. Among all worldwide cases Costa Rica is a good laboratory for studying turnout oscillations. During three decades between 1958 and 1994, political participation average rates remained high in a comparative perspective. Following that trend, one would easily predict that individuals socialized during that period of time must replicate automatically their parents' and grandparents' levels of high political activism. However, turnout patterns in the country since 1998 do not fit very well in that story.Older voters are no longer voting at the rates they usually did and the younger are entering into politics during times of lower participation. The combination of these two factors can have big deleterious and long-lasting effects on turnout trends.Estimating the causal relationship between consecutive voting decisions has proven to be intrinsically difficult for social scientists. Drawing on an exceptionally rich and unique turnout dataset and a mixed-methods approach that includes longitudinal multivariate analysis, face-toface interviews and geospatial statistics this contribution seeks to explain why in Costa Rica, currently the oldest and most stable democracy in Latin America, turnout has declined? And more importantly: what factors drive these changes? v Individual characteristics, although still relevant in static theories regarding turnout determinants, have proved to be insufficient for understanding why individuals' turnout behavior varies over time. Instead, I theorize that the partisan (group) identity that makes people turn out because they are loyal to the party in a context of conflict produces stronger motivation but it is activated selectively, and it only works in a context of "threat" or polarized deliberation.Nevertheless, these incentives may change over time, they may increase or decrease under certain circumstances impacting turnout. Essentially, the more polarized the electoral competition, the easier it will be for citizens to cast their vote.A polarized deliberation, the key factor in my causal story, creates the conditions for the activation of strong partisan identities that stimulate voters' mobilization to the polls. Therefore, During the course of my fieldwork in Costa Rica, I accumulated many debts. I especially thank all the persons I contacted for the interviews and accepted to share their experiences with me. These interviews were crucial for my research project. Without the knowledge I compiled in these conversations I would not be able to develop the theoretical argument of chapter 6.In Pitt, I was also fortunate to share time with several great friends. (Carlin et.al. 2015).The worst case scenario would be one in which this pattern could extend individuals' apathy toward politics during lifetime, causing low turnout to freeze for decades. Therefore, if we want to understand the implications of turnout decline in established democracies, we first need to comprehend the conditions under which these chang...