This paper explores the causes of invalid voting in Brazilian elections. Given that invalid ballot rates tend to be higher where voting is compulsory, the correlates of invalid votes in those countries deserve attention. In this regard, Brazil provides an ideal case for analysing the issue. Brazil not only has the largest electorate of all democracies with compulsory voting laws, but it has also introduced electronic ballots, what has been responsible for a considerable decline in the invalid vote rates. Using data from ESEB, a public opinion survey on elections, we perform a series of logistic regressions to analyse the 2010 presidential, gubernatorial and parliamentary elections, and evaluate the impact of political disaffection and educational level on invalid voting behaviour. We also test a third explanation that so far has not received much attention of scholars: the sheer lack of preference over the running candidates, regardless of distrust levels. Our analyses find that lack of preference has a significant impact on invalid voting at all government levels. Education is negatively correlated with invalid voting, but it is significant only for the presidential elections, a result that confirms the role of the complexity of Brazilian parliamentary elections on invalid voting. Low evaluation of institutions has an impact only over certain types of elections.
